added information about submission grade

- added logger
- restructured internal dialogs

README.md

@@ -1,3 +1,34 @@
-# JCash
+## JCash
 
-Draft program for the Java class of semester 2. The goal was to simulate basic cash machine that can read customer data from a .csv file and let the user view the data with curde forms of authentication.
+## About
+
+Draft program for the Java class of semester 2. The goal was to simulate basic cash machine that can read customer data from a `.csv` file and let the user view the data with crude forms of authentication.
+
+> This project was graded with 100,0 out of 100,0 points
+
+## Overview
+
+The program can read `.csv` file from disk and allows the user login to an account specified.
+After login, the user can deposit, takeoff or transfer money from an account.
+The application does not write any changes back into the file.
+
+## Images
+
+![preview.png](https://git.teridax.de/dhbw/JCash/raw/branch/main/meta/Preview.png)
+
+## Repository structure
+
+The `meta/` folder only contains metadata required for the README. Its not a build relevant folder.
+Sample database files can be found under `res/`.
+
+## CSV Database format
+
+The first row is always ignored as this is generally contains the columns header.
+
+Reference example:
+
+
+| Bank                 | BLZ    | Kontonummer | PIN  | Kontostand | Kontoart  | Zins | Überziehungsbetrag | Kundennummer | Name    | Vorname | Straße                      |
+| ---------------------- | -------- | ------------- | ------ | ------------ | ----------- | ------ | --------------------- | -------------- | --------- | --------- | ------------------------------ |
+| VR Bank Rhein-Neckar | MA2424 | 4711        | 1234 | 45,90€    | Girokonto |      | 1000€              | 8745364      | Gunther | Peter   | Katzenköttel an der Strulle |
+| Berliner Bank        | 19087  | 987456      | 4578 | 9,05€     | Sparkonto | 3%   |                     | 39845762     | Korb    | Jauch   | Unter der Brücke            |

src/me/teridax/jcash/Logging.java

@@ -0,0 +1,97 @@
+package me.teridax.jcash;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+import java.util.logging.*;
+
+import static java.nio.file.Path.of;
+
+/**
+ * Utility class for providing a global logger for the entire application instance at runtime
+ */
+public final class Logging {
+
+    /**
+     * Publicly available logger instance.
+     */
+    public static final Logger LOGGER = Logger.getLogger(Logging.class.getName());
+
+    /**
+     * Folder the log files are stored in, relative to the file containing the class
+     */
+    private static final String LOG_FOLDER_NAME = "logs/";
+    /**
+     * Format for the date time used for log files
+     */
+    private static final String DATE_TIME_FORMAT = "yyyy-MM-dd_HH-mm-ss";
+
+    /**
+     * Initialize the global system logger.
+     * Adds a file logging handler
+     */
+    static void initializeSystemLogger(Level level) {
+        LogManager.getLogManager().reset();
+
+        createConsoleLogger(level);
+        createFileLogger(level);
+
+        LOGGER.setLevel(level);
+    }
+
+    /**
+     * Add a console log handler writing to the applications stderr
+     *
+     * @param level the level to set the handler to
+     */
+    private static void createConsoleLogger(Level level) {
+        ConsoleHandler ch = new ConsoleHandler();
+        ch.setLevel(level);
+        LOGGER.addHandler(ch);
+    }
+
+    /**
+     * Create a log handler writing to a file.
+     * The file will be located in a folder directly besides the application
+     * with the name LOG_FOLDER_NAME. The name will follow the format DATE_TIME_FORMAT plus "log" as
+     * file extension.
+     *
+     * @param level the log level to set the handler to
+     */
+    private static void createFileLogger(Level level) {
+        // setup log file name
+        LocalDateTime now = LocalDateTime.now();
+        String dateTime = DateTimeFormatter.ofPattern(DATE_TIME_FORMAT).format(now);
+        String logFileName = LOG_FOLDER_NAME + dateTime + ".log";
+
+        // setup the folder for the logs
+        initializeLogFolder();
+
+        try {
+            FileHandler fh = new FileHandler(logFileName);
+            fh.setLevel(level);
+            LOGGER.addHandler(fh);
+        } catch (Exception e) {
+            LOGGER.warning("Unable to initialize logging for file: " + logFileName);
+        }
+    }
+
+    /**
+     * Checks if the folder containing log files is present.
+     * If the folder does not exist, the function will create a new folder.
+     */
+    private static void initializeLogFolder() {
+        Path folderPath = of(LOG_FOLDER_NAME);
+
+        if (Files.isDirectory(folderPath))
+            return;
+
+        try {
+            Files.createDirectory(folderPath);
+        } catch (IOException e) {
+            LOGGER.warning("Unable to create directory: " + folderPath);
+        }
+    }
+}

src/me/teridax/jcash/Main.java

@@ -1,10 +1,19 @@
 package me.teridax.jcash;
 
+import me.teridax.jcash.gui.IconProvider;
 import me.teridax.jcash.gui.Loader;
-import me.teridax.jcash.gui.account.AccountController;
-import me.teridax.jcash.gui.login.LoginController;
+import me.teridax.jcash.gui.MainFrame;
+import me.teridax.jcash.gui.Utils;
+import me.teridax.jcash.lang.Locales;
 
 import javax.swing.*;
+import java.awt.*;
+import java.io.IOException;
+import java.util.Objects;
+import java.util.logging.Level;
+
+import static me.teridax.jcash.Logging.LOGGER;
+import static me.teridax.jcash.Logging.initializeSystemLogger;
 
 public final class Main {
 
@@ -14,24 +23,99 @@ public final class Main {
     private static Main instance;
 
     /**
-     * Primary window of this program
+     * Primary class for controlling GUI of this application
      */
-    private final JFrame window;
+    private final MainFrame window;
 
     private Main() {
-        // create main window and set defaults
-        this.window = new JFrame();
-        this.window.setTitle("Bankautomat");
-        this.window.setLocationByPlatform(true);
-        this.window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.window = new MainFrame();
+    }
+
+    /**
+     * Prompts the user a dialog to select a file to load the database from.
+     * If a valid database has been read a login screen will be shown.
+     * If no file was selected or the database was invalid the application will close.
+     */
+    public void loadDatabase() {
+        try {
+            var bms = Loader.load();
+            this.window.setBms(bms);
+
+        } catch (Exception e) {
+            LOGGER.severe("Failed to load database: " + e.getMessage());
+            Utils.error("Failed to load database");
+            System.exit(1);
+        }
     }
 
     public static void main(String[] args) {
+        initializeSystemLogger(Level.FINE);
+
+        setPlatformDependingTheme();
+
+        loadExtraFont();
+
+        Locales.autodetectDefaultLocale();
+
         // create main instance and show the login screen
         instance();
-        getInstance().showLoginScreen();
+        getInstance().loadDatabase();
     }
 
+    /**
+     * Loads the extra font file used on the login button
+     */
+    private static void loadExtraFont() {
+        try {
+            var font = Font.createFont(Font.TRUETYPE_FONT, Objects.requireNonNull(IconProvider.class.getResourceAsStream("res/Circus.ttf")));
+            GraphicsEnvironment ge = GraphicsEnvironment.getLocalGraphicsEnvironment();
+            ge.registerFont(font);
+        } catch (IOException | FontFormatException | NullPointerException e) {
+            LOGGER.warning("Could not load font file: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Set the look and feel via the ui manager.
+     * This function will select a look and feel so that the application will
+     * look most like a native application.
+     * It will select the systems look and feel for Windows and MacOS
+     * and GTK for unix based systems.
+     */
+    private static void setPlatformDependingTheme() {
+        // default look and feel
+        var laf = UIManager.getCrossPlatformLookAndFeelClassName();
+
+        // runtime os
+        String os = System.getProperty("os.name").toLowerCase();
+        LOGGER.fine("Detected operating system: " + os);
+
+        // set look and feel class name depending on the platform we run on
+        if (os.contains("win") || os.contains("mac")) {
+            LOGGER.info("Detected Windows or MacOS based operating system, using system look and feel");
+            laf = UIManager.getSystemLookAndFeelClassName();
+        } else if (os.contains("nix") || os.contains("nux") || os.contains("aix") || os.contains("sunos")) {
+            LOGGER.info("Detected Unix/Linux based operating system, using GTK look and feel");
+            laf = "com.sun.java.swing.plaf.gtk.GTKLookAndFeel";
+        } else {
+            LOGGER.warning("Unable to detect operating system: " + os);
+        }
+
+        try {
+            LOGGER.info("Setting look and feel to class: " + laf);
+            UIManager.setLookAndFeel(laf);
+        } catch (ClassNotFoundException | UnsupportedLookAndFeelException e) {
+            LOGGER.severe("Look and feel class not found: " + e.getMessage());
+        } catch (InstantiationException | IllegalAccessException e) {
+            LOGGER.warning("Could not set look and feel: " + e.getMessage());
+        }
+    }
+
+    /**
+     * Get the main singleton instance of this program
+     *
+     * @return the singleton instance of this class
+     */
     public static Main getInstance() {
         return instance;
     }
@@ -39,55 +123,28 @@ public final class Main {
     /**
      * Attempts to create a new instance of the singleton class Main.
      * This method throws an exception if the class is already instantiated.
+     *
      * @throws IllegalStateException if the class is already instantiated
-     * @pre the static instance of this class should be null.
-     * @post the static instance of this class will be set
      */
     public static void instance() {
         if (null != instance)
             throw new IllegalStateException(Main.class.getName() + " is already initialized");
 
+        LOGGER.fine("Creating singleton instance of class " + Main.class.getName());
+
         Main.instance = new Main();
     }
 
-    /**
-     * Shows the open dialog for selecting a database file. After selection, it then proceeds to prompt login.
-     * Afterward the selected account can be managed.
-     * This method is non-blocking and all work described is performed asynchronously on the AWT Event dispatcher.
-     */
-    public void showLoginScreen() {
-        SwingUtilities.invokeLater(() -> {
-            try {
-                // select db file
-                var path = Loader.load();
-                // read database and login
-                var login = new LoginController(path);
-
-                // when we have logged in set the account viewer as window content
-                login.addAccountSelectionListener(account -> {
-                    var profileCont = new AccountController(account, login.getData().getBms());
-                    this.window.setContentPane(profileCont.getView());
-                    this.window.revalidate();
-                    this.window.repaint();
-                });
-
-                // we are not logged in yet, so show the login prompt on the main window
-                this.window.setContentPane(login.getView());
-                this.window.setSize(800, 600);
-                this.window.setVisible(true);
-
-            } catch (IllegalStateException e) {
-                System.out.println("no file selected. goodbye");
-                System.exit(0);
-            }
-        });
+    public JFrame getWindow() {
+        return this.window.getWindow();
     }
 
     /**
-     * Logs the user out of the database, hiding the main window.
+     * Logs the user out of the currently open account.
+     * This will show the login mask and clear the password field or the previous
+     * login attempt.
      */
     public void logout() {
-        window.setContentPane(new JLabel("you're logged out"));
-        window.setVisible(false);
+        this.window.logout();
     }
 }

src/me/teridax/jcash/banking/Bank.java

@@ -1,5 +1,11 @@
 package me.teridax.jcash.banking;
 
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.Owner;
+import me.teridax.jcash.banking.management.Profile;
+import me.teridax.jcash.gui.Utils;
+
 import java.util.*;
 import java.util.regex.Pattern;
 
@@ -23,12 +29,29 @@ public final class Bank {
      */
     private final Map<Owner, Set<Account>> accounts;
 
-    Bank(String blz, String name) {
+    public Bank(String blz, String name) {
         this.blz = blz;
         this.name = name;
         this.accounts = new HashMap<>();
     }
 
+    /**
+     * Validates the given BLZ. If the blz is not valid an exception is thrown.
+     *
+     * @param maybeBlz a string to be tested for being a blz
+     * @return returns the correctly formatted blz
+     * @throws IllegalArgumentException if the supplied argument is not a valid blz
+     */
+    public static String validateBlz(String maybeBlz) throws IllegalArgumentException {
+        var pattern = Pattern.compile("[\\w-_]+");
+        var matcher = pattern.matcher(maybeBlz);
+
+        if (matcher.find())
+            return matcher.group();
+
+        throw new IllegalArgumentException("not a valid BLZ: " + maybeBlz);
+    }
+
     public String getBlz() {
         return blz;
     }
@@ -41,7 +64,8 @@ public final class Bank {
      * Add a new account and its associated owner to this bank.
      * If the owner is already present the account is added to the existing owner.
      * If the account is already present for the owner the old account gets overwritten.
-     * @param owner the owner of the account
+     *
+     * @param owner   the owner of the account
      * @param account the account of the owner
      */
     public void addAccount(Owner owner, Account account) {
@@ -65,6 +89,7 @@ public final class Bank {
 
     /**
      * Retrieve all accounts owned by the specific owner.
+     *
      * @param owner the owner for which accounts are to be retrieved
      * @return all accounts owned by the owner and managed by this bank
      */
@@ -72,24 +97,9 @@ public final class Bank {
         return accounts.get(owner).toArray(Account[]::new);
     }
 
-    /**
-     * Validates the given BLZ. If the blz is not valid an exception is thrown.
-     * @param maybeBlz a string to be tested for being a blz
-     * @return returns the correctly formatted blz
-     * @throws IllegalArgumentException if the supplied argument is not a valid blz
-     */
-    public static String validateBlz(String maybeBlz) throws IllegalArgumentException {
-        var pattern = Pattern.compile("[\\w-_]+");
-        var matcher = pattern.matcher(maybeBlz);
-
-        if (matcher.find())
-            return matcher.group();
-
-        throw new IllegalArgumentException("not a valid BLZ: " + maybeBlz);
-    }
-
     /**
      * Return a profile of the specified international bank account number.
+     *
      * @param iban the number to create a profile for
      * @return the profile for the iban account
      */
@@ -103,6 +113,7 @@ public final class Bank {
                 }
             }
         }
+        Logging.LOGGER.finer("Account not found: " + iban);
         return Optional.empty();
     }
 }

src/me/teridax/jcash/banking/BankTest.java

@@ -0,0 +1,26 @@
+package me.teridax.jcash.banking;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
+
+public class BankTest {
+
+    @Test
+    public void testBlzValidation() {
+        // everything is fine
+        assertEquals(Bank.validateBlz("MA2424"), "MA2424");
+        assertEquals(Bank.validateBlz("VR-BANK-567"), "VR-BANK-567");
+        assertEquals(Bank.validateBlz("19087"), "19087");
+
+        // cut stuff away
+        assertEquals(Bank.validateBlz("MA2%asd424"), "MA2");
+        assertEquals(Bank.validateBlz("qg0948 z67 0"), "qg0948");
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testBlzValidationException() {
+        assertNotEquals(Bank.validateBlz("öüäöüäöü"), "öüäöüäöü");
+    }
+}

src/me/teridax/jcash/banking/CurrentAccount.java

@@ -1,22 +0,0 @@
-package me.teridax.jcash.banking;
-
-/**
- * Immutable currency account storing only overdraft.
- * English equivalent to "Girokonto"
- */
-public final class CurrentAccount extends Account {
-
-    /**
-     * Overdraft amount in currency.
-     */
-    private final double overdraft;
-
-    public CurrentAccount(int iban, int pin, double balance, double overdraft) {
-        super(iban, pin, balance);
-        this.overdraft = overdraft;
-    }
-
-    public double getOverdraft() {
-        return overdraft;
-    }
-}

src/me/teridax/jcash/banking/accounts/Account.java

@@ -1,9 +1,12 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.accounts;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
 
+import static me.teridax.jcash.lang.Translator.translate;
+
 /**
  * Base class for bank accounts.
  * Stores the iban, pin and balance.
@@ -14,15 +17,15 @@ public abstract class Account {
     /**
      * International bank account number
      */
-    private final int iban;
+    protected final int iban;
     /**
      * Personal identification number
      */
-    private final int pin;
+    protected final int pin;
     /**
      * Balance of this account
      */
-    private double balance;
+    protected double balance;
 
     public Account(int iban, int pin, double balance) {
         this.iban = iban;
@@ -33,13 +36,15 @@ public abstract class Account {
     /**
      * Parses a row of a fixed amount of columns into an account.
      * This function will attempt to create an instance of two classes which inherit from Account.
+     *
      * @param columns array of 6 strings
-     * @return either an instance of {@link me.teridax.jcash.banking.SavingsAccount} or an instance of {@link me.teridax.jcash.banking.CurrentAccount}
+     * @return either an instance of {@link SavingsAccount} or an instance of {@link CurrentAccount}
      * @throws IllegalArgumentException if the account type cannot be determined or the provided data is invalid
-     * @throws NullPointerException if columns is null
+     * @throws NullPointerException     if columns is null
      */
     public static Account fromColumns(String[] columns) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(columns);
+        Logging.LOGGER.finer("Parsing account from columns");
 
         // deserialize fields
         var iban = StringDecoder.decodeUniqueIdentificationNumber(columns[0]);
@@ -50,15 +55,20 @@ public abstract class Account {
         // try to detect the specific runtime class to deserialize
         try {
             if (type.equals("Sparkonto")) {
+                Logging.LOGGER.fine("Account detected as Sparkonto");
                 var interest = StringDecoder.decodePercent(columns[4]);
                 return new SavingsAccount(iban, pin, balance, interest);
             } else if (type.equals("Girokonto")) {
+                Logging.LOGGER.fine("Account detected as Girokonto");
                 var overdraft = StringDecoder.decodeCurrency(columns[5]);
                 return new CurrentAccount(iban, pin, balance, overdraft);
             } else {
+                Logging.LOGGER.severe("Account type could not be detected");
                 throw new IllegalArgumentException("Invalid account type: " + type);
             }
+
         } catch (IllegalArgumentException | NullPointerException e) {
+            Logging.LOGGER.severe("Account field could not be decoded: " + e.getMessage());
             throw new IllegalArgumentException("Account format: ", e);
         }
     }
@@ -80,10 +90,17 @@ public abstract class Account {
         return Objects.hash(iban);
     }
 
+    /**
+     * Returns true if the parameter is an instance of class {@link Account} and both their
+     * ibans are equal.
+     *
+     * @param obj the obj to compare to
+     * @return true if the parameter is an instance of class {@link Account} and their ibans match
+     */
     @Override
     public boolean equals(Object obj) {
         if (obj instanceof Account)
-            return iban == ((Account)obj).iban;
+            return iban == ((Account) obj).iban;
 
         return false;
     }
@@ -92,13 +109,25 @@ public abstract class Account {
      * Returns a description of the account in form a string.
      * This method is not equal to {@link #toString()} but is intended to be
      * a method used to retrieve a formatted representation for guis.
+     *
      * @return a basic description of the account in form a string
      */
     public String getDescription() {
-        return String.format("%s (%s)", iban, getClass().getSimpleName());
+        return String.format("%s (%s)", iban, translate(getClass().getSimpleName()));
     }
 
-    public void deposit(double amount) {
+    /**
+     * Add a non-negative value onto the balance of this account.
+     *
+     * @param amount the amount of value to add
+     * @throws IllegalArgumentException if amount is negative
+     */
+    public void deposit(double amount) throws IllegalArgumentException {
+        if (amount < 0) {
+            Logging.LOGGER.severe("Cannot deposit negative amount of money: " + amount);
+            throw new IllegalArgumentException("amount must be positive");
+        }
+
         this.balance += amount;
     }
 
@@ -110,9 +139,16 @@ public abstract class Account {
     /**
      * Takeoff a certain amount of money from this accounts balance.
      * Saturates the result if the value to subtract is greater than the balance present.
+     *
      * @param amount the amount of money to subtract from the accounts balance
+     * @throws IllegalArgumentException if amount is greater than the balance present
      */
-    public void takeoff(double amount) {
-        this.balance = Math.max(0, this.balance - amount);
+    public void takeoff(double amount) throws IllegalArgumentException {
+        if (amount > this.balance) {
+            Logging.LOGGER.severe("Cannot take off more money than present in balance: " + amount);
+            throw new IllegalArgumentException("amount must be smaller or equals the accounts balance");
+        }
+
+        this.balance = this.balance - amount;
     }
 }

src/me/teridax/jcash/banking/accounts/CurrentAccount.java

@@ -0,0 +1,49 @@
+package me.teridax.jcash.banking.accounts;
+
+import me.teridax.jcash.Logging;
+
+/**
+ * Immutable currency account storing only overdraft.
+ * English equivalent to "Girokonto"
+ */
+public final class CurrentAccount extends Account {
+
+    /**
+     * Overdraft amount in currency.
+     */
+    private final double overdraft;
+
+    public CurrentAccount(int iban, int pin, double balance, double overdraft) {
+        super(iban, pin, balance);
+        this.overdraft = overdraft;
+    }
+
+    public double getOverdraft() {
+        return overdraft;
+    }
+
+    /**
+     * Takeoff a certain amount of money from this accounts balance.
+     * Saturates the result if the value to subtract is greater than the balance present.
+     *
+     * @param amount the amount of money to subtract from the accounts balance
+     * @throws IllegalArgumentException if amount is smaller than 0 or the overflow is greater than the overdraft.
+     */
+    @Override
+    public void takeoff(double amount) throws IllegalArgumentException {
+        Logging.LOGGER.fine("taking off money: " + amount + " from account: " + iban);
+
+        var overflow = amount - getBalance();
+
+        if (overflow > 0) {
+            Logging.LOGGER.fine("taking off money with overflow: " + overflow);
+
+            if (overflow > overdraft) {
+                Logging.LOGGER.warning("amount to takeoff greater than overdraft");
+                throw new IllegalArgumentException("amount to takeoff greater than overdraft");
+            }
+        }
+
+        this.balance -= amount;
+    }
+}

src/me/teridax/jcash/banking/accounts/Owner.java

@@ -1,5 +1,6 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.accounts;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
@@ -33,17 +34,20 @@ public final class Owner {
 
     /**
      * Create a new instance of this class parsed from the columns.
+     *
      * @param columns the fields of this class as strings
      * @return an instance of this class
      * @throws IllegalArgumentException if the supplied columns is invalid
-     * @throws NullPointerException if columns is null
+     * @throws NullPointerException     if columns is null
      */
     public static Owner fromColumns(String... columns) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(columns);
+        Logging.LOGGER.finer("parsing owner from columns");
 
         if (columns.length != 6)
             throw new IllegalArgumentException("Invalid number of columns: " + columns.length);
 
+        Logging.LOGGER.finer("Decoding owner fields");
         // decode fields
         var uid = StringDecoder.decodeUniqueIdentificationNumber(columns[0]);
         var familyName = StringDecoder.decodeName(columns[1]);
@@ -86,9 +90,9 @@ public final class Owner {
 
     @Override
     public boolean equals(Object obj) {
-        if (obj instanceof Owner) {
+        if (obj instanceof Owner)
             return this.uid == ((Owner) obj).getUid();
-        }
+
         return false;
     }
 

src/me/teridax/jcash/banking/accounts/SavingsAccount.java

@@ -1,4 +1,4 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.accounts;
 
 /**
  * Savings account representing a german "Sparkonto".

src/me/teridax/jcash/banking/management/BankingManagementSystem.java

@@ -1,12 +1,19 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.management;
 
+import me.teridax.jcash.banking.Bank;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.Owner;
 import me.teridax.jcash.decode.StringDecoder;
 
 import java.io.IOException;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.*;
 
+import static me.teridax.jcash.Logging.LOGGER;
+
 /**
  * Management system for banks and all accounts provided by these banks and their respective account owners.
  * This class serves a read only database which can only modify runtime data without any respect to CRUD or the ACID
@@ -14,6 +21,18 @@ import java.util.*;
  */
 public final class BankingManagementSystem {
 
+    /**
+     * Separator used to separate columns of CSV files
+     */
+    private static final String SEPARATOR = ";";
+    /**
+     * Charsets to try when decoding the source file
+     */
+    private static final Charset[] ENCODINGS = {
+            StandardCharsets.UTF_8,
+            Charset.forName("windows-1252")
+    };
+
     /**
      * A set of banks
      */
@@ -26,6 +45,7 @@ public final class BankingManagementSystem {
     /**
      * Utility method for retrieving the tail of a string array.
      * This method return all items which follow the n-th index denoted by index.
+     *
      * @param array the array to take the tail of
      * @param index the amount trailing indices to skip
      * @return an array containing the last elements of the supplied array
@@ -56,25 +76,30 @@ public final class BankingManagementSystem {
      * </ol>
      * The file can contain a header line which gets skipped when reading.
      * Note that the first line is always skipped and the name of every column is not checked in any way.
+     *
      * @param file the file to parse
-     * @throws IllegalArgumentException if the file cannot be read or the containing data is invalid
      * @return a valid BMS
+     * @throws IllegalArgumentException if the file cannot be read or the containing data is invalid
      */
     public static BankingManagementSystem loadFromCsv(Path file) throws IllegalArgumentException {
+        LOGGER.fine("parsing banking management system from file: " + Objects.toString(file, "null"));
         try {
             var bms = new BankingManagementSystem();
-            var content = Files.readString(file);
+            var content = getSource(file);
 
             // read line by line
             // and skip the first line
             content.lines().skip(1).forEach(line -> {
+
+                LOGGER.finest("splitting lines by separator: " + SEPARATOR);
                 // split the line into columns
-                var columns = line.split(";");
+                var columns = line.split(SEPARATOR);
 
                 // one line must contain exactly 14 columns
                 if (columns.length != 14)
                     throw new IllegalArgumentException("invalid column count: " + columns.length);
 
+                LOGGER.finer("reading members from line: " + line);
                 // read basic fields
                 var owner = Owner.fromColumns(tail(columns, 8));
                 var account = Account.fromColumns(tail(columns, 2));
@@ -87,8 +112,10 @@ public final class BankingManagementSystem {
 
                 var bankOfSet = bms.banks.stream().filter(b -> b.equals(bankOfLine)).findFirst();
                 if (bankOfSet.isPresent()) {
+                    LOGGER.fine("bank from current line is already present in management system");
                     bankOfSet.get().addAccount(owner, account);
                 } else {
+                    LOGGER.fine("bank from current line is new for management system");
                     bankOfLine.addAccount(owner, account);
                     bms.banks.add(bankOfLine);
                 }
@@ -96,15 +123,36 @@ public final class BankingManagementSystem {
 
             return bms;
 
-        } catch (IOException e) {
-            throw new IllegalArgumentException("Could not read file " + file, e);
         } catch (IllegalArgumentException | NullPointerException e) {
+            LOGGER.severe("Could not parse file: " + file + " due to: " + e.getMessage());
             throw new IllegalArgumentException("Could not parse file " + file, e);
         }
     }
 
+    /**
+     * Attempts to read the entire file into a string.
+     * This method tires out all encodings in {@link #ENCODINGS}
+     * @param file the file to read
+     * @throws IllegalArgumentException if the file cannot be read
+     * @return the content of the file
+     */
+    private static String getSource(Path file) throws IllegalArgumentException {
+        Exception lastException = null;
+        for (var encoding : ENCODINGS) {
+            try {
+                return Files.readString(file, encoding);
+            } catch (IOException e) {
+                LOGGER.severe("Could not read file: " + file + " due to: " + e.getMessage());
+                lastException = e;
+            }
+        }
+        assert lastException != null;
+        throw new IllegalArgumentException("Invalid encoding, or IO exception: " + lastException.getMessage());
+    }
+
     /**
      * Return a bank with the given blz.
+     *
      * @param blz the blz to search bank of
      * @return the bank with this blz or none
      */

src/me/teridax/jcash/banking/management/BankingManagementSystemTest.java

@@ -1,10 +1,10 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.management;
 
 import org.junit.Test;
 
 import java.nio.file.Paths;
 
-public class DataClassTests {
+public class BankingManagementSystemTest {
 
     @Test
     public void test() {

src/me/teridax/jcash/banking/management/Profile.java

@@ -1,4 +1,11 @@
-package me.teridax.jcash.banking;
+package me.teridax.jcash.banking.management;
+
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.Bank;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.Owner;
+
+import java.util.Arrays;
 
 /**
  * Groups an owner and all of its accounts registered at a specific bank together.
@@ -8,12 +15,29 @@ package me.teridax.jcash.banking;
  */
 public class Profile {
 
+    /**
+     * Owner of the primary account and all other accounts registered at a specific bank
+     */
     private final Owner owner;
+    /**
+     * The bank that manages every account referenced by this profile
+     */
     private final Bank bank;
-    private Account primaryAccount;
+    /**
+     * All other account registered at a specific bank for the specified owner
+     */
     private final Account[] accounts;
+    /**
+     * Primary or currently selected account.
+     */
+    private Account primaryAccount;
 
     public Profile(Owner owner, Bank bank, Account account, Account[] accounts) {
+        if (!Arrays.asList(accounts).contains(account)) {
+            Logging.LOGGER.severe("Account not found:" + account.getDescription());
+            throw new IllegalArgumentException("Primary account is not registered at the bank");
+        }
+
         this.owner = owner;
         this.bank = bank;
         this.accounts = accounts;
@@ -24,6 +48,22 @@ public class Profile {
         return primaryAccount;
     }
 
+    /**
+     * Set the primary account of this profile based on a descriptive text.
+     * This method may not change anything if no account can be found with a matching description
+     *
+     * @param description the description to find a matching account for
+     */
+    public void setPrimaryAccount(String description) {
+        for (Account account : accounts) {
+            if (account.getDescription().equals(description)) {
+                this.primaryAccount = account;
+                break;
+            }
+        }
+        Logging.LOGGER.warning("Account " + description + " not found in associated account list");
+    }
+
     public Owner getOwner() {
         return owner;
     }
@@ -35,18 +75,4 @@ public class Profile {
     public Account[] getAccounts() {
         return accounts;
     }
-
-    /**
-     * Set the primary account of this profile based on a descriptive text.
-     * This method may not change anything if no account can be found with a matching description
-     * @param description the description to find a matching account for
-     */
-    public void setPrimaryAccount(String description) {
-        for (Account account : accounts) {
-            if (account.getDescription().equals(description)) {
-                this.primaryAccount = account;
-                break;
-            }
-        }
-    }
 }

src/me/teridax/jcash/decode/DecodeTests.java

@@ -0,0 +1,67 @@
+package me.teridax.jcash.decode;
+
+import me.teridax.jcash.lang.Locales;
+import org.junit.Test;
+
+import static junit.framework.TestCase.assertEquals;
+import static me.teridax.jcash.decode.StringDecoder.*;
+
+public class DecodeTests {
+    @Test
+    public void testDecodeSuccessfulFunctions() {
+        // make sure a comma separated integer from fractions
+        Locales.setDefaultLocale("de", "DE");
+
+        assertEquals(decodePercent("1,003"), 100.3d, 1e-3d);
+
+        decodeUniqueIdentificationNumber("9578647895");
+        decodeUniqueIdentificationNumber("    927856347   ");
+        decodeUniqueIdentificationNumber("0");
+        decodeUniqueIdentificationNumber("'9578647895");
+
+        decodeName("Adolf");
+        decodeName("Günther");
+        decodeName("Saßkia");
+
+        decodeStreet("Bahnhofstraße 40/1");
+        decodeStreet("Gülleweg 9");
+        decodeStreet("Echsengaße 67 / 4");
+
+        assertEquals(decodePercent("1,4%"), 1.4, 1e-3d);
+        assertEquals(decodePercent("99"), 9900.0d);
+        assertEquals(decodePercent("1,003%"), 1.003, 1e-5d);
+        assertEquals(decodePercent("1,003"), 100.3, 1e-5d);
+        assertEquals(decodePercent("'1,003"), 100.3, 1e-5d);
+
+        assertEquals(decodeCurrency("1,3€"), 1.3d);
+        assertEquals(decodeCurrency("‘0567€"), 567d);
+        assertEquals(decodeCurrency("145,34"), 145, 34d);
+        assertEquals(decodeCurrency("0,45   €"), 0.45d);
+    }
+
+    @Test
+    public void decodeLocaleDependent() {
+        Locales.setDefaultLocale("de", "DE");
+        assertEquals(decodeCurrency("13.00,45€"), 1300.45);
+
+        Locales.setDefaultLocale("en", "EN");
+        assertEquals(decodeCurrency("13,00.45€"), 1300.45);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void testDecodeInvalidFunctions() {
+        decodeUniqueIdentificationNumber("q0948tvb6q047t 740   t74z0tz    784");
+        decodeUniqueIdentificationNumber("-39867.8475");
+        decodeUniqueIdentificationNumber("-398678475");
+        decodeUniqueIdentificationNumber(" ß9qu908t76q34798t6q734vb9843");
+
+        decodeName("John Doe");
+        decodeName("3490qt67v 0b34");
+        decodeName("Alexander9");
+        decodeName("-ga76re78g6$§");
+
+        decodeStreet("Bahnhofstraße -40/1");
+        decodeStreet("Gülleweg 9//567");
+        decodeStreet("23Echsengaße 67 / 4 Hofwetg 9");
+    }
+}

src/me/teridax/jcash/decode/StringDecoder.java

@@ -1,63 +1,105 @@
 package me.teridax.jcash.decode;
 
-import org.junit.Test;
+import me.teridax.jcash.lang.Locales;
 
+import javax.swing.text.NumberFormatter;
 import java.text.NumberFormat;
 import java.text.ParseException;
-import java.util.Locale;
 import java.util.Objects;
 import java.util.regex.Pattern;
 
-import static junit.framework.TestCase.assertEquals;
-
 /**
  * Utility class for converting various single line strings into a specific data type according
  * to a format mostly dictated by a locale.
  */
 public class StringDecoder {
 
+    public static NumberFormat getNumberFormat() {
+        return NumberFormat.getInstance(Locales.getDefaultLocale());
+    }
+
     /**
-     * Locale to use when converting strings
+     * Returns a NumberFormatter for parsing double values in the appropriate locale.
+     * @return the number formatter
      */
-    private static final Locale LOCALE = Locale.GERMANY;
+    public static NumberFormatter getNumberFormatter(double maxValue) {
+        var formatter = new NumberFormatter();
+        formatter.setValueClass(Double.class);
+        formatter.setMinimum(0d);
+        formatter.setMaximum(maxValue);
+        formatter.setAllowsInvalid(true);
+        formatter.setCommitsOnValidEdit(true);
+
+        return formatter;
+    }
+
     /**
-     * NumberFormat to use when converting strings
+     * Returns a NumberFormatter for parsing integer values in the appropriate locale.
+     * @return the number formatter
      */
-    public static final NumberFormat LOCAL_NUMBER_FORMAT = NumberFormat.getInstance(LOCALE);
+    public static NumberFormatter getIntegerNumberFormatter() {
+        var formatter = new NumberFormatter();
+        formatter.setValueClass(Integer.class);
+        formatter.setMinimum(0d);
+        formatter.setAllowsInvalid(true);
+        formatter.setCommitsOnValidEdit(true);
+
+        return formatter;
+    }
 
     /**
      * Attempts to convert the given string into a double value representing a percentage.
-     * The percentage is stored in the range [0,1] and can linearly be mapped to [0, 100] by multiplying with 100.
+     * The output value will be in the range [0, 100]. Strings formatted without a percentage
+     * symbol will be assumed to be normalized and thus multiplied by 100 to retrieve the result in percent.
+     *
      * @param number the string to convert
      * @return the double value
      * @throws IllegalArgumentException when the format is invalid
-     * @throws NullPointerException when the argument is null
+     * @throws NullPointerException     when the argument is null
      */
     public static double decodePercent(String number) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(number);
 
-        // trim the number and cut out optional percent symbols
-        var trimmed = number.trim().replace("%", "");
+        // trim and cut out weird leading single quotes for numbers
+        var prepared = number.trim().replaceAll("^\\s*['‘`](?=\\d)", "");
 
-        try {
-            return LOCAL_NUMBER_FORMAT.parse(trimmed).doubleValue();
-        } catch (ParseException ex) {
-            throw new IllegalArgumentException("Not a valid number: " + number, ex);
+        var pattern = Pattern.compile("^([^%]+)?(%)?$", Pattern.CASE_INSENSITIVE);
+        var matcher = pattern.matcher(prepared);
+        if (matcher.find()) {
+            // if no percentage symbol is given the number will be multiplied by 100%
+            var scale = 1e2;
+
+            // check if capture group 2 captured a percentage symbol
+            // if to we don't want to apply any scaling to the value
+            if (null != matcher.group(2))
+                scale = 1;
+
+            try {
+                return getNumberFormat().parse(matcher.group(1)).doubleValue() * scale;
+            } catch (ParseException ex) {
+                throw new IllegalArgumentException("Not a valid number: " + number, ex);
+            }
+        } else {
+            throw new IllegalArgumentException("not a valid percentage");
         }
     }
 
     /**
      * Attempts to convert the given string into a currency value.
+     *
      * @param currency the string to convert
      * @return the double value
      * @throws IllegalArgumentException when the format is invalid
-     * @throws NullPointerException when the argument is null
+     * @throws NullPointerException     when the argument is null
      */
     public static double decodeCurrency(String currency) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(currency);
 
+        // trim and cut out weird leading single quotes for numbers
+        var prepared = currency.trim().replaceAll("^\\s*['‘`](?=\\d)", "");
+
         try {
-            return LOCAL_NUMBER_FORMAT.parse(currency.trim()).doubleValue();
+            return getNumberFormat().parse(prepared).doubleValue();
         } catch (ParseException ex) {
             throw new IllegalArgumentException("Not a valid currency in german locale: " + currency, ex);
         }
@@ -66,19 +108,21 @@ public class StringDecoder {
     /**
      * Attempts to convert the given string into universally unique number.
      * This function does not check for duplicates. The number must be a positive integer.
+     *
      * @param number the string to convert
      * @return the integer serial number
      * @throws IllegalArgumentException when the format is invalid
-     * @throws NullPointerException when the argument is null
+     * @throws NullPointerException     when the argument is null
      */
     public static int decodeUniqueIdentificationNumber(String number) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(number);
 
+        // trim and cut out weird leading single quotes for numbers
+        var preparedUID = number.trim().replaceAll("^\\s*['‘`](?=\\d)", "");
+
         // check if the string is a valid unsigned number
         try {
-            LOCAL_NUMBER_FORMAT.setParseIntegerOnly(true);
-            var serialNumber = LOCAL_NUMBER_FORMAT.parse(number.trim());
-            LOCAL_NUMBER_FORMAT.setParseIntegerOnly(false);
+            var serialNumber = getNumberFormat().parse(preparedUID);
 
             if (serialNumber.intValue() < 0)
                 throw new IllegalArgumentException("Not a valid unique identification number: " + number);
@@ -92,17 +136,18 @@ public class StringDecoder {
     /**
      * Attempts to convert the given string into a name.
      * This method performs validation and trimming.
+     *
      * @param name the string to convert
      * @return the qualified name
      * @throws IllegalArgumentException when the format is invalid
-     * @throws NullPointerException when the argument is null
+     * @throws NullPointerException     when the argument is null
      */
     public static String decodeName(String name) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(name);
 
         var trimmed = name.trim();
 
-        var pattern = Pattern.compile("[\\w-\\s]+", Pattern.CASE_INSENSITIVE);
+        var pattern = Pattern.compile("[^\\d]+", Pattern.CASE_INSENSITIVE);
         var matcher = pattern.matcher(trimmed);
         if (matcher.find()) {
             return matcher.group();
@@ -113,15 +158,16 @@ public class StringDecoder {
 
     /**
      * Attempts to convert the given string into a street and an optional house address.
+     *
      * @param street the string to convert
      * @return the address name
      * @throws IllegalArgumentException when the format is invalid
-     * @throws NullPointerException when the argument is null
+     * @throws NullPointerException     when the argument is null
      */
     public static String decodeStreet(String street) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(street);
 
-        var pattern = Pattern.compile("\\S+(\\s+\\d+(/\\d+)?)?", Pattern.CASE_INSENSITIVE);
+        var pattern = Pattern.compile("\\S+(\\s+\\d+(\\s*/\\s*\\d+)?)?", Pattern.CASE_INSENSITIVE);
         var matcher = pattern.matcher(street);
         if (matcher.find()) {
             return matcher.group();
@@ -129,44 +175,4 @@ public class StringDecoder {
             throw new IllegalArgumentException("not a void address");
         }
     }
-
-    @Test
-    public void testDecodeSuccessfulFunctions() {
-        decodeUniqueIdentificationNumber("95786978625347895");
-        decodeUniqueIdentificationNumber("    927856347   ");
-        decodeUniqueIdentificationNumber("0");
-
-        decodeName("Adolf");
-        decodeName("Günther");
-        decodeName("Saßkia");
-
-        decodeStreet("Bahnhofstraße 40/1");
-        decodeStreet("Gülleweg 9");
-        decodeStreet("Echsengaße 67 / 4");
-
-        assertEquals(decodePercent("1,4%"), 1.4d);
-        assertEquals(decodePercent("99"), 99.0d);
-        assertEquals(decodePercent("1,003  %"), 1.003d);
-
-        assertEquals(decodeCurrency("1,3€"), 1.3d);
-        assertEquals(decodeCurrency("145,34"), 145,34d);
-        assertEquals(decodeCurrency("0,45   €"), 0.45d);
-    }
-
-    @Test(expected = IllegalArgumentException.class)
-    public void testDecodeInvalidFunctions() {
-        decodeUniqueIdentificationNumber("q0948tvb6q047t 740   t74z0tz    784");
-        decodeUniqueIdentificationNumber("-39867.8475");
-        decodeUniqueIdentificationNumber("-398678475");
-        decodeUniqueIdentificationNumber(" ß9qu908t76q34798t6q734vb9843");
-
-        decodeName("John Doe");
-        decodeName("3490qt67v 0b34");
-        decodeName("Alexander9");
-        decodeName("-ga76re78g6$§");
-
-        decodeStreet("Bahnhofstraße -40/1");
-        decodeStreet("Gülleweg 9//567");
-        decodeStreet("23Echsengaße 67 / 4 Hofwetg 9");
-    }
 }

src/me/teridax/jcash/gui/IconProvider.java

@@ -0,0 +1,50 @@
+package me.teridax.jcash.gui;
+
+import javax.imageio.ImageIO;
+import java.awt.*;
+import java.awt.image.BufferedImage;
+import java.util.Objects;
+
+import static me.teridax.jcash.Logging.LOGGER;
+
+/**
+ * Static class for providing the capabilities to load images from file.
+ */
+public class IconProvider {
+
+    private static final Image DEFAULT_IMAGE = new BufferedImage(256, 256, BufferedImage.TYPE_INT_RGB);
+
+    /**
+     * Fetches the windows icon.
+     * @return the windows icon
+     */
+    public static Image getWindowIcon() {
+        return loadIcon("res/register.png");
+    }
+
+    /**
+     * Loads the specified image from disk.
+     * If the file cannot be made into an image because its corrupted or the file cannot be read,
+     * the default image is returned {@link #DEFAULT_IMAGE}
+     * @param path the path to the image
+     * @return the specified image or {@link #DEFAULT_IMAGE}
+     */
+    private static Image loadIcon(String path) {
+        try {
+            var is = Objects.requireNonNull(IconProvider.class.getResourceAsStream(path));
+            return ImageIO.read(is);
+        } catch (Exception e) {
+            LOGGER.severe("Unable to load icon " + path + " because: " + e.getMessage());
+        }
+
+        return DEFAULT_IMAGE;
+    }
+
+    /**
+     * Fetches the background image used for the login screen
+     * @return login screen background image
+     */
+    public static Image getBackground() {
+        return loadIcon("res/background.png");
+    }
+}

src/me/teridax/jcash/gui/InvalidInputException.java

@@ -0,0 +1,21 @@
+package me.teridax.jcash.gui;
+
+
+/**
+ * Exception thrown when some user input is invalid
+ */
+@SuppressWarnings("unused")
+public class InvalidInputException extends IllegalStateException {
+
+    public InvalidInputException(String message, Exception cause) {
+        super(message, cause);
+    }
+
+    public InvalidInputException(String message) {
+        super(message);
+    }
+
+    public InvalidInputException(Exception cause) {
+        super(cause);
+    }
+}

src/me/teridax/jcash/gui/Loader.java

@@ -1,12 +1,14 @@
 package me.teridax.jcash.gui;
 
-import me.teridax.jcash.banking.BankingManagementSystem;
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.Main;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
 
 import javax.swing.*;
 import javax.swing.filechooser.FileNameExtensionFilter;
-import java.io.File;
 
 import static javax.swing.JFileChooser.APPROVE_OPTION;
+import static me.teridax.jcash.lang.Translator.translate;
 
 /**
  * Utility class for loading a BMS configuration from a csv file.
@@ -16,13 +18,15 @@ public class Loader {
     /**
      * Filter that only allows for files with *.csv extension
      */
-    private static final FileNameExtensionFilter FILE_FILTER = new FileNameExtensionFilter("Comma separated value spreadsheet", "csv", "CSV");
+    private static final FileNameExtensionFilter FILE_FILTER = new FileNameExtensionFilter(translate("Comma separated value spreadsheet"), "csv", "CSV");
 
-    private Loader() {}
+    private Loader() {
+    }
 
     /**
      * Load a BMS from a csv file. Opens up a dialog which prompts the user to select a single file.
      * Once the file is selected this function will try to parse the contents to a BMS and return the instance.
+     *
      * @return a valid BMS instance loaded from a file
      * @throws IllegalStateException When either no file is selected or the selected files content is invalid
      */
@@ -33,9 +37,8 @@ public class Loader {
         fileChooser.setFileFilter(FILE_FILTER);
         fileChooser.setDialogType(JFileChooser.OPEN_DIALOG);
         fileChooser.setAcceptAllFileFilterUsed(false);
-        fileChooser.setCurrentDirectory(new File("/home/teridax/IdeaProjects/JCash/res"));
 
-        if (fileChooser.showDialog(null, "Load database") == APPROVE_OPTION) {
+        if (fileChooser.showDialog(Main.getInstance().getWindow(), translate("Load database")) == APPROVE_OPTION) {
             // parse file content
             try {
                 return BankingManagementSystem.loadFromCsv(fileChooser.getSelectedFile().toPath());
@@ -44,6 +47,7 @@ public class Loader {
             }
         }
 
+        Logging.LOGGER.warning("no file selected");
         throw new IllegalStateException("No file selected");
     }
 }

src/me/teridax/jcash/gui/MainFrame.java

@@ -0,0 +1,128 @@
+package me.teridax.jcash.gui;
+
+import me.teridax.jcash.banking.management.BankingManagementSystem;
+import me.teridax.jcash.gui.account.AccountController;
+import me.teridax.jcash.gui.login.LoginController;
+import me.teridax.jcash.lang.Locales;
+
+import javax.swing.*;
+import java.awt.*;
+import java.util.Objects;
+
+import static me.teridax.jcash.Logging.LOGGER;
+import static me.teridax.jcash.lang.Translator.translate;
+
+public class MainFrame {
+
+    /**
+     * Constant used to identify the login screen on the cardlayout
+     */
+    private static final String LOGIN_SCREEN_STRING_IDENT = "LoginScreen";
+    /**
+     * Constant used to identify the profile screen on the cardlayout
+     */
+    private static final String PROFILE_SCREEN_STRING_IDENT = "ProfileScreen";
+    /**
+     * Version of this application
+     */
+    private static final String VERSION = "v2.1.0";
+
+    /**
+     * Primary window of this program
+     */
+    private final JFrame window;
+    /**
+     * Primary layout of this application
+     */
+    private final CardLayout layout;
+
+    /**
+     * Database containing every bank, account and owner available
+     */
+    private BankingManagementSystem bms;
+
+    private LoginController loginMask;
+    private AccountController accountController;
+
+    public MainFrame() {
+        // create main window and set defaults
+        this.window = new JFrame();
+        this.window.setTitle(translate("Cashmachine") + getInfoString());
+        this.window.setLocationByPlatform(true);
+        this.window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        this.window.setIconImage(IconProvider.getWindowIcon());
+
+        this.layout = new CardLayout();
+        this.window.getContentPane().setLayout(this.layout);
+
+        initialize();
+    }
+
+
+    /**
+     * Creates and returns a general information string about this application
+     * @return the locale and the current version as string
+     */
+    private String getInfoString() {
+        return " locale: [" + Locales.getDefaultLocale().toString() + "] " + VERSION;
+    }
+
+    /**
+     * Initializes the GUI components of login screen and profile view
+     */
+    private void initialize() {
+        // create the login mask
+
+        this.loginMask = new LoginController();
+
+        // when we have logged in set the account viewer as window content
+        this.loginMask.addAccountSelectionListener(account -> {
+            LOGGER.finer("account selected: " + Objects.toString(account, "null"));
+            accountController.setProfile(account, bms);
+            layout.show(window.getContentPane(), PROFILE_SCREEN_STRING_IDENT);
+        });
+
+        this.window.getContentPane().add(loginMask.getView(), LOGIN_SCREEN_STRING_IDENT);
+
+        // create the account viewer
+
+        this.accountController = new AccountController();
+        this.window.getContentPane().add(accountController.getView(), PROFILE_SCREEN_STRING_IDENT);
+    }
+
+    /**
+     * Sets the BMS of this application to use for the GUI.
+     * This method will show the login screen to the user
+     * @param bms the BMS to use for the GUI
+     */
+    public void setBms(BankingManagementSystem bms) {
+        this.bms = bms;
+        this.loginMask.setBankingManagementSystem(bms);
+        this.showLoginScreen();
+        this.window.pack();
+        this.window.setResizable(false);
+        this.window.setLocationRelativeTo(null);
+        this.window.setVisible(true);
+    }
+
+    /**
+     * Shows the open dialog for selecting a database file. After selection, it then proceeds to prompt login.
+     * Afterward the selected account can be managed.
+     * This method is non-blocking and all work described is performed asynchronously on the AWT Event dispatcher.
+     */
+    private void showLoginScreen() {
+        this.layout.show(this.window.getContentPane(), LOGIN_SCREEN_STRING_IDENT);
+    }
+
+    /**
+     * Logs the user out of the database, hiding the main window.
+     */
+    public void logout() {
+        this.loginMask.logout();
+        this.layout.show(this.window.getContentPane(), LOGIN_SCREEN_STRING_IDENT);
+    }
+
+    public JFrame getWindow() {
+        return this.window;
+    }
+}

src/me/teridax/jcash/gui/Utils.java

@@ -0,0 +1,86 @@
+package me.teridax.jcash.gui;
+
+import me.teridax.jcash.Main;
+import me.teridax.jcash.lang.Locales;
+
+import javax.swing.*;
+import java.awt.*;
+import java.text.Format;
+import java.text.NumberFormat;
+
+public class Utils {
+
+    /**
+     * Formats the string so that it will be displayed as a Heading 1 element by JLabels.
+     * This embeds the given string into two html tags.
+     * Note that eny html entities in the string will be formatted as valid HTML entities.
+     * Meaning they won't show up in as plain text.
+     * @param title the title to format.
+     * @return the given string embedded into <pre>&lt;html>&lt;h1>$string&lt;/h1>&lt;/html></pre>
+     */
+    public static String addHeading(String title) {
+        return String.format("<html><h1>%s</h1></html>", title);
+    }
+
+    /**
+     * Add a new row of components to the specified target component.
+     * This will add label to the right side of the next row and the specified component to the left.
+     *
+     * @param constraints the constraint to use. Must be non-null
+     * @param target      the base component to add a row to
+     * @param comp        the component to add to the left side
+     * @param row         the row to add the components to
+     * @param name        the labels text to add to the left side
+     */
+    public static void addGridBagRow(GridBagConstraints constraints, JComponent target, JComponent comp, int row, String name) {
+        constraints.gridwidth = 1;
+        constraints.gridx = 1;
+        constraints.gridy = row;
+        constraints.weightx = 0;
+        constraints.fill = GridBagConstraints.HORIZONTAL;
+        target.add(new JLabel(name, SwingConstants.RIGHT), constraints);
+
+        if (comp == null)
+            return;
+
+        constraints.gridx = 2;
+        constraints.gridy = row;
+        constraints.weightx = 1;
+        constraints.fill = GridBagConstraints.HORIZONTAL;
+        target.add(comp, constraints);
+    }
+
+    /**
+     * Add a new row of components to the specified target component.
+     * This will add label to the right side of the next row and the specified component to the left.
+     *
+     * @param constraints the constraint to use. Must be non-null
+     * @param target      the base component to add a row to
+     * @param comp        the component to add to the left side
+     * @param row         the row to add the components to
+     * @param right       the component to place on the left side
+     */
+    public static void addGridBagRow(GridBagConstraints constraints, JComponent target, JComponent comp, int row, Component right) {
+        constraints.gridwidth = 1;
+        constraints.gridx = 1;
+        constraints.gridy = row;
+        constraints.weightx = 0;
+        constraints.fill = GridBagConstraints.HORIZONTAL;
+        target.add(right, constraints);
+
+        constraints.gridx = 2;
+        constraints.gridy = row;
+        constraints.weightx = 1;
+        constraints.fill = GridBagConstraints.HORIZONTAL;
+        target.add(comp, constraints);
+    }
+
+    /**
+     * Opens an error message dialog. This function will block the calling thread until the error message
+     * disposed.
+     * @param message the message to show to the user
+     */
+    public static void error(String message) {
+        JOptionPane.showMessageDialog(Main.getInstance().getWindow(), message, "Error occurred", JOptionPane.ERROR_MESSAGE);
+    }
+}

src/me/teridax/jcash/gui/account/AccountController.java

@@ -1,11 +1,12 @@
 package me.teridax.jcash.gui.account;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.Main;
-import me.teridax.jcash.banking.BankingManagementSystem;
-import me.teridax.jcash.banking.Profile;
-import me.teridax.jcash.gui.deposit.DepositDialog;
-import me.teridax.jcash.gui.takeoff.TakeoffDialog;
-import me.teridax.jcash.gui.transfer.TransferDialog;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
+import me.teridax.jcash.banking.management.Profile;
+import me.teridax.jcash.gui.deposit.DepositController;
+import me.teridax.jcash.gui.takeoff.TakeoffController;
+import me.teridax.jcash.gui.transfer.TransferController;
 
 /**
  * Controller for controlling the gui of an account.
@@ -17,31 +18,73 @@ public class AccountController {
      */
     private final AccountView view;
 
-    public AccountController(Profile profile, BankingManagementSystem bms) {
-        this.view = new AccountView();
-        this.view.setProfile(profile);
-        this.data = new AccountData(bms);
+    private Profile profile;
 
-        createListeners(profile);
+    public AccountController() {
+        this.view = new AccountView();
+        this.data = new AccountData();
     }
 
-    private void createListeners(Profile profile) {
-        this.view.getAccountSelection().addActionListener(e -> {
-            var description = ((String) this.view.getAccountSelection().getSelectedItem());
-            profile.setPrimaryAccount(description);
-            this.view.setProfile(profile);
-        });
+    /**
+     * Sets the profile and BMS used to manage banking.
+     * @param profile the profile used to manage the account
+     * @param bms the BMS used access other banking accounts
+     */
+    public void setProfile(Profile profile, BankingManagementSystem bms) {
+        this.profile = profile;
+        this.view.setProfile(profile);
+        this.data.setBms(bms);
+        this.createListeners();
+    }
 
-        this.view.getLogout().addActionListener(e -> {
-            Main.getInstance().logout();
-            Main.getInstance().showLoginScreen();
-        });
+    /**
+     * Create listeners for GUI components
+     */
+    private void createListeners() {
+        this.view.getAccountSelection().addActionListener(e -> changeAccount());
+        this.view.getLogout().addActionListener(e -> logout());
+        this.view.getDeposit().addActionListener(e -> depositMoney());
+        this.view.getTakeoff().addActionListener(e -> takeoffMoney());
+        this.view.getTransfer().addActionListener(e -> transferMoney());
+    }
 
-        this.view.getDeposit().addActionListener(e -> new DepositDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile)));
+    /**
+     * Open dialog to deposit money
+     */
+    private void depositMoney() {
+        new DepositController(profile.getPrimaryAccount());
+        this.view.updateAccountVariables(profile);
+    }
 
-        this.view.getTakeoff().addActionListener(e -> new TakeoffDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile)));
+    /**
+     * Open dialog to transfer money
+     */
+    private void transferMoney() {
+        new TransferController(profile.getPrimaryAccount(), data.getBms());
+        this.view.updateAccountVariables(profile);
+    }
 
-        this.view.getTransfer().addActionListener(e -> new TransferDialog(profile.getPrimaryAccount(), data.getBms(), () -> this.view.setProfile(profile)));
+    /**
+     * Open dialog to take off money
+     */
+    private void takeoffMoney() {
+        new TakeoffController(profile.getPrimaryAccount());
+        this.view.updateAccountVariables(profile);
+    }
+
+    private void logout() {
+        Logging.LOGGER.fine("Logging out of account");
+        Main.getInstance().logout();
+    }
+
+    /**
+     * Change the selected account.
+     */
+    private void changeAccount() {
+        var description = ((String) this.view.getAccountSelection().getSelectedItem());
+        Logging.LOGGER.fine("Changing primary account selected: " + description);
+        this.profile.setPrimaryAccount(description);
+        this.view.setProfile(profile);
     }
 
     public AccountView getView() {

src/me/teridax/jcash/gui/account/AccountData.java

@@ -1,16 +1,19 @@
 package me.teridax.jcash.gui.account;
 
-import me.teridax.jcash.banking.BankingManagementSystem;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
 
+/**
+ * Data storage class for account management
+ */
 public class AccountData {
 
-    private final BankingManagementSystem bms;
-
-    public AccountData(BankingManagementSystem bms) {
-        this.bms = bms;
-    }
+    private BankingManagementSystem bms;
 
     public BankingManagementSystem getBms() {
         return bms;
     }
+
+    public void setBms(BankingManagementSystem bms) {
+        this.bms = bms;
+    }
 }

src/me/teridax/jcash/gui/account/AccountView.java

@@ -1,12 +1,20 @@
 package me.teridax.jcash.gui.account;
 
-import me.teridax.jcash.banking.*;
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.CurrentAccount;
+import me.teridax.jcash.banking.accounts.SavingsAccount;
+import me.teridax.jcash.banking.management.Profile;
 import me.teridax.jcash.decode.StringDecoder;
 
 import javax.swing.*;
 import java.awt.*;
+import java.util.Arrays;
+import java.util.Comparator;
 
 import static javax.swing.SwingConstants.RIGHT;
+import static me.teridax.jcash.gui.Utils.addGridBagRow;
+import static me.teridax.jcash.lang.Translator.translate;
 
 public class AccountView extends JPanel {
 
@@ -29,63 +37,47 @@ public class AccountView extends JPanel {
         createComponents();
         createLayout();
 
-        setBorder(BorderFactory.createEmptyBorder(8,8,8,8));
+        setBorder(BorderFactory.createEmptyBorder(8, 8, 8, 8));
     }
 
+    /**
+     * The profile to manage via the GUI.
+     * @param profile the profile to manage
+     */
     public void setProfile(Profile profile) {
-        var bank = profile.getBank();
-        var account = profile.getPrimaryAccount();
-        var owner = profile.getOwner();
-
-        this.blz.setText(bank.getBlz());
-        this.bankName.setText(bank.getName());
-
-        this.iban.setText(String.valueOf(account.getIban()));
-        this.name.setText(owner.getName() + " " + owner.getFamilyName());
-        this.address.setText(owner.getStreet() + " " + owner.getCity());
-
-        this.balance.setText(StringDecoder.LOCAL_NUMBER_FORMAT.format(account.getBalance()) + " €");
-
-        this.type.setText(account.getClass().getSimpleName());
-        if (account instanceof CurrentAccount) {
-            this.typeSpecialLabel.setText("Overdraft");
-            this.typeSpecialProperty.setText( StringDecoder.LOCAL_NUMBER_FORMAT.format(((CurrentAccount) account).getOverdraft()) + " €");
-        } else if (account instanceof SavingsAccount) {
-            this.typeSpecialLabel.setText("Interest rate");
-            this.typeSpecialProperty.setText( ((SavingsAccount) account).getInterest() + " %" );
-        }
+        this.updateAccountVariables(profile);
 
         this.accountSelection.removeAllItems();
 
-        for (var otherAccount : profile.getAccounts()) {
-            this.accountSelection.addItem(otherAccount.getDescription());
-        }
-        this.accountSelection.setSelectedItem(account.getDescription());
+        var accounts = profile.getAccounts();
+        Arrays.stream(accounts).sorted(Comparator.comparingInt(Account::getIban)).forEach(a -> this.accountSelection.addItem(a.getDescription()));
+
+        this.accountSelection.setSelectedItem(profile.getPrimaryAccount().getDescription());
     }
 
     private void createLayout() {
         var content = new JPanel(new GridBagLayout());
 
-        this.setLayout(new BorderLayout(16, 16));
+        this.setLayout(new BorderLayout(12, 12));
         this.add(new JScrollPane(content), BorderLayout.CENTER);
 
         var constraints = new GridBagConstraints();
 
         constraints.gridwidth = 4;
-        constraints.insets = new Insets(12,12,12,12);
+        constraints.insets = new Insets(12, 12, 12, 12);
 
         var accountSelectionPanel = new JPanel(new BorderLayout(12, 0));
         accountSelectionPanel.add(iban, BorderLayout.CENTER);
         accountSelectionPanel.add(accountSelection, BorderLayout.EAST);
 
-        addInputRow(constraints, content, accountSelectionPanel, 1, new JLabel("IBAN", RIGHT));
-        addInputRow(constraints, content, name, 2, new JLabel("Name/Family-name", RIGHT));
-        addInputRow(constraints, content, address, 3, new JLabel("Address", RIGHT));
-        addInputRow(constraints, content, bankName, 4, new JLabel("Bank", RIGHT));
-        addInputRow(constraints, content, blz, 5, new JLabel("BLZ", RIGHT));
-        addInputRow(constraints, content, type, 6, new JLabel("Account", RIGHT));
-        addInputRow(constraints, content, typeSpecialProperty, 7, typeSpecialLabel);
-        addInputRow(constraints, content, balance, 8, new JLabel("Balance", RIGHT));
+        addGridBagRow(constraints, content, accountSelectionPanel, 1, translate("IBAN"));
+        addGridBagRow(constraints, content, name, 2, translate("Name/Family-name"));
+        addGridBagRow(constraints, content, address, 3, translate("Address"));
+        addGridBagRow(constraints, content, bankName, 4, translate("Bank"));
+        addGridBagRow(constraints, content, blz, 5, translate("BLZ"));
+        addGridBagRow(constraints, content, type, 6, translate("Account"));
+        addGridBagRow(constraints, content, typeSpecialProperty, 7, typeSpecialLabel);
+        addGridBagRow(constraints, content, balance, 8, translate("Balance"));
 
         var buttonPanel = Box.createHorizontalBox();
         buttonPanel.add(Box.createHorizontalStrut(4));
@@ -123,34 +115,10 @@ public class AccountView extends JPanel {
 
         this.accountSelection = new JComboBox<>();
 
-        this.logout = new JButton("Logout");
-        this.transfer = new JButton("Transfer");
-        this.deposit = new JButton("Deposit");
-        this.takeoff = new JButton("Takeoff");
-    }
-
-    /**
-     * Add a new row of components to the specified target component.
-     * This will add label to the right side of the next row and the specified component to the left.
-     * @param constraints the constraint to use. Must be non-null
-     * @param target the base component to add a row to
-     * @param comp the component to add to the left side
-     * @param row the row to add the components to
-     * @param label the label to add to the left side
-     */
-    private void addInputRow(GridBagConstraints constraints, JComponent target, JComponent comp, int row, JLabel label) {
-        constraints.gridwidth = 1;
-        constraints.gridx = 1;
-        constraints.gridy = row;
-        constraints.weightx = 0;
-        constraints.fill = GridBagConstraints.HORIZONTAL;
-        target.add(label, constraints);
-
-        constraints.gridx = 2;
-        constraints.gridy = row;
-        constraints.weightx = 1;
-        constraints.fill = GridBagConstraints.HORIZONTAL;
-        target.add(comp, constraints);
+        this.logout = new JButton(translate("Logout"));
+        this.transfer = new JButton(translate("Transfer"));
+        this.deposit = new JButton(translate("Deposit"));
+        this.takeoff = new JButton(translate("Takeoff"));
     }
 
     public JComboBox<String> getAccountSelection() {
@@ -172,4 +140,40 @@ public class AccountView extends JPanel {
     public JButton getTakeoff() {
         return takeoff;
     }
+
+    /**
+     * Writes the accessible class fields of the primary account
+     * into the text fields. Also updates the combo box for
+     * all associated accounts.
+     * @param profile the profile to update from
+     */
+    public void updateAccountVariables(Profile profile) {
+        Logging.LOGGER.finer("Updating account view");
+        // temporarily extract data
+        var bank = profile.getBank();
+        var account = profile.getPrimaryAccount();
+        var owner = profile.getOwner();
+
+        this.blz.setText(bank.getBlz());
+        this.bankName.setText(bank.getName());
+
+        this.iban.setText(String.valueOf(account.getIban()));
+        this.name.setText(owner.getName() + " " + owner.getFamilyName());
+        this.address.setText(owner.getStreet() + " " + owner.getCity());
+
+        this.balance.setText(StringDecoder.getNumberFormat().format(account.getBalance()) + " €");
+
+        // update account type specific fields
+
+        this.type.setText(translate(account.getClass().getSimpleName()));
+        if (account instanceof CurrentAccount) {
+            this.typeSpecialLabel.setText(translate("Overdraft"));
+            this.typeSpecialProperty.setText(StringDecoder.getNumberFormat().format(((CurrentAccount) account).getOverdraft()) + " €");
+        } else if (account instanceof SavingsAccount) {
+            this.typeSpecialLabel.setText(translate("Interest rate"));
+            this.typeSpecialProperty.setText(((SavingsAccount) account).getInterest() + " %");
+        } else {
+            Logging.LOGGER.severe("Type of new primary account cannot be determined: " + account.getClass().getName());
+        }
+    }
 }

src/me/teridax/jcash/gui/deposit/DepositController.java

@@ -0,0 +1,84 @@
+package me.teridax.jcash.gui.deposit;
+
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.gui.InvalidInputException;
+import me.teridax.jcash.gui.Utils;
+
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
+import java.text.ParseException;
+
+/**
+ * Class for controlling the deposit operation via a dialog.
+ */
+public class DepositController {
+
+    private final DepositView view;
+    /**
+     * Account to deposit money to.
+     */
+    private final Account account;
+
+    public DepositController(Account account) {
+        this.account = account;
+
+        this.view = new DepositView(account.getBalance());
+
+        this.view.getDeposit().addActionListener(e -> depositMoney());
+        this.view.getCancel().addActionListener(e -> view.dispose());
+        this.view.getValue().getDocument().addDocumentListener(new DocumentListener() {
+
+            /**
+             * Validate the amount to deposit and update display
+             * variables.
+             */
+            private void validateInputState() {
+                var balance = account.getBalance();
+                try {
+                    view.getValue().commitEdit();
+                    var amount = view.getAmount();
+                    view.setCommittedValue(amount, balance + amount);
+                    view.getDeposit().setEnabled(true);
+                } catch (InvalidInputException | ParseException ex) {
+                    view.setCommittedValue(0, balance);
+                    view.getDeposit().setEnabled(false);
+                }
+            }
+
+            @Override
+            public void insertUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void removeUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void changedUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+        });
+        this.view.showDialog();
+    }
+
+    /**
+     * Deposit the last valid value to the account.
+     * This method may display error dialogs when no money can be deposited.
+     */
+    private void depositMoney() {
+        try {
+            var amount = view.getAmount();
+            Logging.LOGGER.fine("Depositing money of account: " + account.getIban() + " amount: " + amount);
+            account.deposit(amount);
+        } catch (IllegalArgumentException ex) {
+            Logging.LOGGER.severe("Cannot deposit money of account: " + account.getIban() + " because: " + ex.getMessage());
+            Utils.error(ex.getMessage());
+        } catch (InvalidInputException ex) {
+            Utils.error(ex.getMessage());
+        }
+        view.dispose();
+    }
+}

src/me/teridax/jcash/gui/deposit/DepositDialog.java

@@ -1,17 +0,0 @@
-package me.teridax.jcash.gui.deposit;
-
-import me.teridax.jcash.banking.Account;
-
-public class DepositDialog {
-
-    public DepositDialog(Account account, Runnable onDeposit) {
-        var view = new DepositView();
-        view.getDeposit().addActionListener(e -> {
-            account.deposit(view.getAmount());
-            onDeposit.run();
-            view.dispose();
-        });
-        view.getCancel().addActionListener(e -> view.dispose());
-        view.showDialog();
-    }
-}

src/me/teridax/jcash/gui/deposit/DepositView.java

@@ -1,29 +1,52 @@
 package me.teridax.jcash.gui.deposit;
 
-import me.teridax.jcash.banking.Account;
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
+import me.teridax.jcash.gui.IconProvider;
+import me.teridax.jcash.gui.InvalidInputException;
 
 import javax.swing.*;
 import java.awt.*;
-import java.text.NumberFormat;
 import java.text.ParseException;
 
+import static me.teridax.jcash.lang.Translator.translate;
+
+/**
+ * View class for displaying a dialog prompting the user to
+ * enter a valid amount to deposit at their account
+ */
 public class DepositView {
 
+    /**
+     * Window to use
+     */
     private JDialog dialog;
     private JButton cancel;
+    /**
+     * Button for applying the deposit operation
+     */
     private JButton deposit;
+    /**
+     * Displays the validated value to deposit
+     */
+    private JLabel enteredValue;
+    /**
+     * Displays the account balance after the deposit operation
+     */
+    private JLabel balanceAfterDeposit;
     private JFormattedTextField value;
 
-    public DepositView() {
-        createComponents();
+    public DepositView(double maxValue) {
+        createComponents(maxValue);
         layoutComponents();
     }
 
     public void showDialog() {
+        dialog.setIconImage(IconProvider.getWindowIcon());
         dialog.setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
-        dialog.setTitle("Deposit money");
+        dialog.setTitle(translate("Deposit money"));
         dialog.pack();
+        dialog.setSize(dialog.getWidth() * 2, dialog.getHeight());
         dialog.setResizable(false);
         dialog.setLocationRelativeTo(null);
         dialog.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
@@ -37,70 +60,103 @@ public class DepositView {
 
         c.gridx = 0;
         c.gridy = 0;
-        c.weightx = 1;
-        c.weighty = 1;
-        c.gridwidth = 3;
-        c.fill = GridBagConstraints.HORIZONTAL;
-        c.anchor = GridBagConstraints.CENTER;
-        c.insets = new Insets(4, 4, 4, 4);
-        dialog.getContentPane().add(new JLabel("Deposit money"), c);
-
-        c.gridx = 0;
-        c.gridy = 1;
         c.gridwidth = 1;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0;
-        dialog.getContentPane().add(new JLabel("Value", SwingConstants.RIGHT), c);
+        c.insets = new Insets(6, 6, 6, 6);
+        dialog.getContentPane().add(new JLabel(translate("Value"), SwingConstants.RIGHT), c);
 
         c.gridx = 1;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0.5;
         dialog.getContentPane().add(value, c);
 
         c.gridx = 2;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LINE_START;
         c.weightx = 0;
         dialog.getContentPane().add(new JLabel("€"), c);
 
+        c.gridx = 0;
+        c.gridy = 1;
+        c.gridwidth = 1;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(new JLabel(translate("Value to deposit:"), SwingConstants.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 1;
+        c.gridwidth = 2;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(enteredValue, c);
+
+        c.gridx = 0;
+        c.gridy = 2;
+        c.gridwidth = 1;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(new JLabel(translate("Balance after deposit:"), SwingConstants.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 2;
+        c.gridwidth = 2;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(balanceAfterDeposit, c);
+
         var buttonPanel = new JPanel(new FlowLayout(FlowLayout.TRAILING));
         buttonPanel.add(cancel);
         buttonPanel.add(deposit);
 
         c.gridx = 0;
-        c.gridy = 2;
+        c.gridy = 3;
         c.gridwidth = 3;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
-        c.insets = new Insets(10, 10, 10, 10);
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents() {
+    private void createComponents(double maxValue) {
         this.dialog = new JDialog();
 
-        this.cancel = new JButton("Cancel");
-        this.deposit = new JButton("Deposit");
-        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
+        this.cancel = new JButton(translate("Cancel"));
+        this.deposit = new JButton(translate("Deposit"));
+        this.value = new JFormattedTextField(StringDecoder.getNumberFormatter(Double.MAX_VALUE));
+        this.enteredValue = new JLabel();
+        this.balanceAfterDeposit = new JLabel(StringDecoder.getNumberFormat().format(maxValue));
+
+        this.deposit.setEnabled(false);
 
         this.dialog.setContentPane(new JPanel(new GridBagLayout()));
     }
 
-    public double getAmount() {
+    /**
+     * Returns the amount of money that should be deposited
+     * This value derives from the input of the user.
+     * @return the value to deposit
+     * @throws InvalidInputException if the user entered something invalid
+     */
+    public double getAmount() throws InvalidInputException {
         if (value.getText().isBlank())
-            return 0;
+            throw new InvalidInputException("currency value is blank or has been invalid whilst entered");
 
         try {
-            return NumberFormat.getNumberInstance().parse(value.getText()).doubleValue();
+            return StringDecoder.getNumberFormat().parse(value.getText()).doubleValue();
         } catch (ParseException e) {
-            throw new RuntimeException(e);
+            Logging.LOGGER.severe("Amount text field contains invalid value: " + value);
+            throw new InvalidInputException(e);
         }
     }
 
+    public JFormattedTextField getValue() {
+        return value;
+    }
+
     public JButton getCancel() {
         return cancel;
     }
@@ -112,4 +168,14 @@ public class DepositView {
     public void dispose() {
         this.dialog.dispose();
     }
+
+    /**
+     * Sets the supplied amount to the preview GUI fields.
+     * @param amount the value to display for value to deposit
+     * @param after the value to display for balance after deposit
+     */
+    public void setCommittedValue(double amount, double after) {
+        enteredValue.setText(StringDecoder.getNumberFormat().format(amount));
+        balanceAfterDeposit.setText(StringDecoder.getNumberFormat().format(after));
+    }
 }

src/me/teridax/jcash/gui/login/AccountSelectionListener.java

@@ -1,15 +1,17 @@
 package me.teridax.jcash.gui.login;
 
-import me.teridax.jcash.banking.Profile;
+import me.teridax.jcash.banking.management.Profile;
 
 /**
  * Listens for changes in a selected account.
  */
+@FunctionalInterface
 public interface AccountSelectionListener {
 
     /**
      * Run when a new account is selected.
      * The selected account is set as the primary account of the profile
+     *
      * @param account the profile for the selected account
      */
     void onAccountSelected(Profile account);

src/me/teridax/jcash/gui/login/LoginController.java

@@ -1,14 +1,12 @@
 package me.teridax.jcash.gui.login;
 
-import me.teridax.jcash.banking.BankingManagementSystem;
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
+import me.teridax.jcash.gui.Utils;
 
-import javax.swing.*;
 import java.awt.event.ActionEvent;
 import java.util.Optional;
 
-import static javax.swing.JOptionPane.ERROR_MESSAGE;
-import static javax.swing.JOptionPane.showMessageDialog;
-
 public class LoginController {
 
     private final LoginView view;
@@ -16,13 +14,17 @@ public class LoginController {
 
     private AccountSelectionListener listener;
 
-    public LoginController(BankingManagementSystem bms) {
+    public LoginController() {
         this.view = new LoginView();
-        this.data = new LoginData(bms);
+        this.data = new LoginData();
 
         addActionListeners();
     }
 
+    public void setBankingManagementSystem(BankingManagementSystem bms) {
+        this.data.setBms(bms);
+    }
+
     private void addActionListeners() {
         this.view.getLogin().addActionListener(this::login);
     }
@@ -32,6 +34,7 @@ public class LoginController {
             var iban = this.view.getIban().getText();
             return Optional.of(Integer.parseUnsignedInt(iban));
         } catch (NumberFormatException e) {
+            Logging.LOGGER.warning("IBAN text field contains invalid value: " + this.view.getIban().getText());
             return Optional.empty();
         }
     }
@@ -41,6 +44,7 @@ public class LoginController {
             var iban = this.view.getPin().getPassword();
             return Optional.of(Integer.parseUnsignedInt(new String(iban)));
         } catch (NumberFormatException e) {
+            Logging.LOGGER.severe("PIN text field contains invalid value: " + String.valueOf(view.getPin().getPassword()));
             return Optional.empty();
         }
     }
@@ -49,13 +53,13 @@ public class LoginController {
         var blz = this.view.getBlz().getText();
         var iban = this.getIban();
         if (iban.isEmpty()) {
-            showMessageDialog(null, "invalid IBAN", "Faulty login attempt", ERROR_MESSAGE);
+            Utils.error("invalid IBAN entered");
             return;
         }
 
         var pin = this.getPin();
         if (pin.isEmpty()) {
-            showMessageDialog(null, "invalid pin", "Faulty login attempt", ERROR_MESSAGE);
+            Utils.error("invalid PIN entered");
             return;
         }
 
@@ -63,8 +67,8 @@ public class LoginController {
         if (account.isPresent()) {
             this.listener.onAccountSelected(account.get());
         } else {
-            showMessageDialog(null, "invalid login credentials", "Faulty login attempt", ERROR_MESSAGE);
-        }
+            Logging.LOGGER.warning("invalid login credentials: " + iban + " / " + pin);
+         }
     }
 
     public void addAccountSelectionListener(AccountSelectionListener listener) {
@@ -78,4 +82,8 @@ public class LoginController {
     public LoginData getData() {
         return data;
     }
+
+    public void logout() {
+        this.view.getPin().setText("");
+    }
 }

src/me/teridax/jcash/gui/login/LoginData.java

@@ -1,38 +1,52 @@
 package me.teridax.jcash.gui.login;
 
-import me.teridax.jcash.banking.BankingManagementSystem;
-import me.teridax.jcash.banking.Profile;
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
+import me.teridax.jcash.banking.management.Profile;
+import me.teridax.jcash.gui.Utils;
 
 import java.util.Optional;
 
 /**
- * Wrapper class for a {@link me.teridax.jcash.banking.BankingManagementSystem}
+ * Wrapper class for a {@link BankingManagementSystem}
  */
 public class LoginData {
 
-    private final BankingManagementSystem bms;
-
-    public LoginData(BankingManagementSystem bms) {
-        this.bms = bms;
-    }
+    private BankingManagementSystem bms;
 
     /**
      * authenticate the specified account with the provided pin.
-     * @param blz the bank identifier
+     *
+     * @param blz  the bank identifier
      * @param iban the account identifier
-     * @param pin the pin for the account to authenticate with
+     * @param pin  the pin for the account to authenticate with
      * @return an optional wrapping the specified account if authentication was successful
      */
     public Optional<Profile> authenticateAccount(String blz, int iban, int pin) {
+        Logging.LOGGER.info("Authenticating account " + iban);
+
         var optionalBank = bms.getBank(blz);
-        if (optionalBank.isEmpty())
+        if (optionalBank.isEmpty()) {
+            Utils.error("Unknown BLZ: " + blz);
             return Optional.empty();
+        }
 
         var profile = optionalBank.get().getAccount(iban);
-        return profile.filter(value -> value.getPrimaryAccount().getPin() == pin);
+        if (profile.isEmpty()) {
+            Utils.error("Unknown account: " + iban);
+            return Optional.empty();
+        }
+
+        var account = profile.filter(value -> value.getPrimaryAccount().getPin() == pin);
+        if (account.isEmpty()) {
+            Utils.error("PIN does not match");
+            return Optional.empty();
+        }
+
+        return account;
     }
 
-    public BankingManagementSystem getBms() {
-        return bms;
+    public void setBms(BankingManagementSystem bms) {
+        this.bms = bms;
     }
 }

src/me/teridax/jcash/gui/login/LoginView.java

@@ -1,12 +1,30 @@
 package me.teridax.jcash.gui.login;
 
-import javax.swing.*;
-import javax.swing.text.NumberFormatter;
-import java.awt.*;
-import java.text.NumberFormat;
+import me.teridax.jcash.gui.IconProvider;
 
+import javax.swing.*;
+import javax.swing.text.*;
+import java.awt.*;
+
+import static me.teridax.jcash.gui.Utils.addGridBagRow;
+import static me.teridax.jcash.gui.Utils.addHeading;
+import static me.teridax.jcash.lang.Translator.translate;
+
+/**
+ * GUI class for login into an account
+ */
 public class LoginView extends JPanel {
 
+    /**
+     * Maximum number of decimal digits that can be stored lossless by a 32-bit signed integer.
+     * N = log10(2^32-1) = 9,632959861146281
+     */
+    private static final int MAX_PIN_DECIMAL_DIGITS = 9;
+    /**
+     * Number of pixels the banner image should be in width
+     */
+    public static final int BANNER_WIDTH = 400;
+
     private JFormattedTextField blz;
     private JFormattedTextField iban;
     private JPasswordField pin;
@@ -18,64 +36,85 @@ public class LoginView extends JPanel {
     }
 
     private void layoutComponents() {
-        var content = new JPanel(new GridBagLayout());
+        var content = new JLabel();
+        content.setIcon(new ImageIcon(IconProvider.getBackground()));
+        content.setLayout(new BorderLayout());
 
-        this.setBorder(BorderFactory.createEmptyBorder(8,8,8,8));
-        this.setLayout(new BorderLayout(16, 16));
+        var loginPane = new JPanel(new GridBagLayout());
+        loginPane.setOpaque(true);
+        content.add(loginPane, BorderLayout.CENTER);
+        content.add(Box.createHorizontalStrut(BANNER_WIDTH), BorderLayout.WEST);
+
+        this.setLayout(new BorderLayout(32, 32));
         this.add(new JScrollPane(content), BorderLayout.CENTER);
-        this.add(new JLabel("Bankautomat"), BorderLayout.NORTH);
 
         var constraints = new GridBagConstraints();
 
         constraints.gridwidth = 4;
-        constraints.insets = new Insets(12,12,12,12);
+        constraints.insets = new Insets(12, 12, 12, 12);
 
-        addInputRow(constraints, content, blz, 1, "BLZ");
-        addInputRow(constraints, content, iban, 2, "IBAN");
-        addInputRow(constraints, content, pin, 3, "PIN");
+        addGridBagRow(constraints, loginPane, new JLabel(addHeading(translate("Cashmachine"))), 0, "");
+        addGridBagRow(constraints, loginPane, blz, 1, translate("BLZ"));
+        addGridBagRow(constraints, loginPane, iban, 2, translate("IBAN"));
+        addGridBagRow(constraints, loginPane, pin, 3, translate("PIN"));
 
         constraints.gridy = 4;
         constraints.anchor = GridBagConstraints.PAGE_END;
         constraints.weightx = 0;
         constraints.fill = GridBagConstraints.NONE;
-        constraints.insets = new Insets(12,12,12,12);
-        content.add(login, constraints);
+        constraints.insets = new Insets(0, 0, 0, 12);
+        loginPane.add(login, constraints);
     }
 
     private void createComponents() {
-        this.blz = new JFormattedTextField("MA2424");
-        this.iban = new JFormattedTextField(getNumberFormat());
-        this.iban.setText("4711");
-        this.pin = new JPasswordField("1234");
-        this.login = new JButton("Login");
+        this.blz = new JFormattedTextField();
+        this.iban = new JFormattedTextField();
+        this.pin = new JPasswordField();
+        this.login = new JButton(translate("Login"));
+
+        // customize login button
+        // this may not work with every swing look and feel
+        this.login.setFont(new Font("Circus", Font.PLAIN, 28));
+        this.login.setBackground(Color.CYAN);
+
+        restrictPasswordToDigits();
+        restrictIbanInput();
     }
 
-    private NumberFormatter getNumberFormat() {
-        var format = NumberFormat.getIntegerInstance();
-        format.setGroupingUsed(false);
+    /**
+     * Adds a document filter onto {@link #pin} that filters out everything that is not a digit.
+     * The filter also restricts the amount of digits that can be entered to {@link #MAX_PIN_DECIMAL_DIGITS}
+     */
+    private void restrictPasswordToDigits() {
+        ((AbstractDocument) this.pin.getDocument()).setDocumentFilter(new DocumentFilter() {
+            @Override
+            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
+                    throws BadLocationException {
+                String newText = fb.getDocument().getText(0, fb.getDocument().getLength()) + text;
 
-        var formatter = new NumberFormatter(format);
-        formatter.setValueClass(Integer.class);
-        formatter.setMinimum(0);
-        formatter.setMaximum(Integer.MAX_VALUE);
-        formatter.setAllowsInvalid(false);
-
-        return formatter;
+                if (newText.matches(String.format("\\d{1,%s}", MAX_PIN_DECIMAL_DIGITS))) {
+                    super.replace(fb, offset, length, text, attrs);
+                }
+            }
+        });
     }
 
-    private void addInputRow(GridBagConstraints constraints, JComponent target, JComponent comp, int row, String name) {
-        constraints.gridwidth = 1;
-        constraints.gridx = 1;
-        constraints.gridy = row;
-        constraints.weightx = 0;
-        constraints.fill = GridBagConstraints.HORIZONTAL;
-        target.add(new JLabel(name, SwingConstants.RIGHT), constraints);
+    /**
+     * Adds a document filter onto {@link #iban} that filters out everything that is not a digit.
+     * The filter also restricts the amount of digits that can be entered to {@link #MAX_PIN_DECIMAL_DIGITS}
+     */
+    private void restrictIbanInput() {
+        ((AbstractDocument) this.iban.getDocument()).setDocumentFilter(new DocumentFilter() {
+            @Override
+            public void replace(FilterBypass fb, int offset, int length, String text, AttributeSet attrs)
+                    throws BadLocationException {
+                String newText = fb.getDocument().getText(0, fb.getDocument().getLength()) + text;
 
-        constraints.gridx = 2;
-        constraints.gridy = row;
-        constraints.weightx = 1;
-        constraints.fill = GridBagConstraints.HORIZONTAL;
-        target.add(comp, constraints);
+                if (newText.matches(String.format("\\d{1,%s}", MAX_PIN_DECIMAL_DIGITS))) {
+                    super.replace(fb, offset, length, text, attrs);
+                }
+            }
+        });
     }
 
     public JTextField getBlz() {

src/me/teridax/jcash/gui/res/image-sources.md

@@ -0,0 +1,4 @@
+https://pixabay.com/vectors/register-cash-register-modern-23666/
+![register](https://cdn.pixabay.com/photo/2012/04/01/17/34/register-23666_960_720.png)
+Font file
+https://www.dafont.com/de/circus.font?text=Login

src/me/teridax/jcash/gui/takeoff/TakeoffController.java

@@ -0,0 +1,86 @@
+package me.teridax.jcash.gui.takeoff;
+
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.CurrentAccount;
+import me.teridax.jcash.gui.InvalidInputException;
+import me.teridax.jcash.gui.Utils;
+
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
+import java.text.ParseException;
+
+/**
+ * Controller class for handling bank account take off.
+ */
+public class TakeoffController {
+
+    /**
+     * Account to take off
+     */
+    private final Account account;
+    /**
+     * GUI object
+     */
+    private final TakeoffView view;
+
+    public TakeoffController(Account account) {
+        this.account = account;
+
+        // add overdraft on top of the maximum amount
+        // a user is allowed to take off
+        var overdraft = 0.0;
+        if (account instanceof CurrentAccount) {
+            overdraft += ((CurrentAccount) account).getOverdraft();
+        }
+
+        TakeoffData data = new TakeoffData(account.getBalance());
+        this.view = new TakeoffView(data.getMaxValue() + overdraft);
+
+        this.view.getTakeoff().addActionListener(e -> takeOff());
+        this.view.getCancel().addActionListener(e -> view.dispose());
+        this.view.getValue().getDocument().addDocumentListener(new DocumentListener() {
+            private void validateInputState() {
+                var balance = account.getBalance();
+                try {
+                    view.getValue().commitEdit();
+                    var amount = view.getAmount();
+                    view.setCommittedValue(amount, balance - amount);
+                    view.getTakeoff().setEnabled(true);
+                } catch (InvalidInputException | ParseException ex) {
+                    view.setCommittedValue(0, balance);
+                    view.getTakeoff().setEnabled(false);
+                }
+            }
+
+            @Override
+            public void insertUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void removeUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void changedUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+        });
+        this.view.showDialog();
+    }
+
+    /**
+     * Attempts to take off some money from an account.
+     */
+    private void takeOff() {
+        try {
+            account.takeoff(view.getAmount());
+        } catch (IllegalArgumentException | InvalidInputException ex) {
+            Logging.LOGGER.severe("Could not take off money: " + ex.getMessage());
+            Utils.error("Reason: " + ex.getMessage());
+        }
+        view.dispose();
+    }
+}

src/me/teridax/jcash/gui/takeoff/TakeoffData.java

@@ -0,0 +1,20 @@
+package me.teridax.jcash.gui.takeoff;
+
+/**
+ * Data class for taking off value from a certain account
+ */
+public class TakeoffData {
+
+    /**
+     * Maximum value a user is allowed to take off
+     */
+    private final double maxValue;
+
+    public TakeoffData(double maxValue) {
+        this.maxValue = maxValue;
+    }
+
+    public double getMaxValue() {
+        return maxValue;
+    }
+}

src/me/teridax/jcash/gui/takeoff/TakeoffDialog.java

@@ -1,17 +0,0 @@
-package me.teridax.jcash.gui.takeoff;
-
-import me.teridax.jcash.banking.Account;
-
-public class TakeoffDialog {
-
-    public TakeoffDialog(Account account, Runnable onTakeoff) {
-        var view = new TakeoffView();
-        view.getTakeoff().addActionListener(e -> {
-            account.takeoff(view.getAmount());
-            onTakeoff.run();
-            view.dispose();
-        });
-        view.getCancel().addActionListener(e -> view.dispose());
-        view.showDialog();
-    }
-}

src/me/teridax/jcash/gui/takeoff/TakeoffView.java

@@ -1,31 +1,42 @@
 package me.teridax.jcash.gui.takeoff;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
+import me.teridax.jcash.gui.IconProvider;
+import me.teridax.jcash.gui.InvalidInputException;
 
 import javax.swing.*;
 import java.awt.*;
-import java.text.NumberFormat;
 import java.text.ParseException;
 
-import static javax.swing.JOptionPane.ERROR_MESSAGE;
-import static javax.swing.JOptionPane.showMessageDialog;
+import static me.teridax.jcash.lang.Translator.translate;
 
+/**
+ * Dialog for taking off money of an account.
+ */
 public class TakeoffView {
 
     private JDialog dialog;
     private JButton cancel;
     private JButton takeoff;
+    private JLabel enteredValue;
+    private JLabel balanceAfterDeposit;
     private JFormattedTextField value;
 
-    public TakeoffView() {
-        createComponents();
+    public TakeoffView(double maxValue) {
+        createComponents(maxValue);
         layoutComponents();
     }
 
+    /**
+     * Makes this dialog visible.
+     */
     public void showDialog() {
+        dialog.setIconImage(IconProvider.getWindowIcon());
         dialog.setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
-        dialog.setTitle("Takeoff money");
+        dialog.setTitle(translate("Takeoff money"));
         dialog.pack();
+        dialog.setSize(dialog.getWidth() * 2, dialog.getHeight());
         dialog.setResizable(false);
         dialog.setLocationRelativeTo(null);
         dialog.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
@@ -37,42 +48,61 @@ public class TakeoffView {
 
         c.gridx = 0;
         c.gridy = 0;
-        c.weightx = 1;
-        c.weighty = 1;
-        c.gridwidth = 3;
-        c.fill = GridBagConstraints.HORIZONTAL;
-        c.anchor = GridBagConstraints.CENTER;
-        c.insets = new Insets(4, 4, 4, 4);
-        dialog.getContentPane().add(new JLabel("Takeoff money"), c);
-
-        c.gridx = 0;
-        c.gridy = 1;
         c.gridwidth = 1;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0;
-        dialog.getContentPane().add(new JLabel("Value", SwingConstants.RIGHT), c);
+        c.insets = new Insets(6,6,6,6);
+        dialog.getContentPane().add(new JLabel(translate("Value"), SwingConstants.RIGHT), c);
 
         c.gridx = 1;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0.5;
         dialog.getContentPane().add(value, c);
 
         c.gridx = 2;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LINE_START;
         c.weightx = 0;
         dialog.getContentPane().add(new JLabel("€"), c);
 
+        c.gridx = 0;
+        c.gridy = 1;
+        c.gridwidth = 1;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(new JLabel(translate("Value to takeoff:"), SwingConstants.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 1;
+        c.gridwidth = 2;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(enteredValue, c);
+
+        c.gridx = 0;
+        c.gridy = 2;
+        c.gridwidth = 1;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(new JLabel(translate("Balance after takeoff:"), SwingConstants.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 2;
+        c.gridwidth = 2;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        dialog.getContentPane().add(balanceAfterDeposit, c);
+
         var buttonPanel = new JPanel(new FlowLayout(FlowLayout.TRAILING));
         buttonPanel.add(cancel);
         buttonPanel.add(takeoff);
 
         c.gridx = 0;
-        c.gridy = 2;
+        c.gridy = 3;
         c.gridwidth = 3;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
@@ -80,29 +110,50 @@ public class TakeoffView {
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents() {
+    /**
+     * The createComponents function creates the components of the dialog.
+     * @param maxValue Set the maximum value of the jformattedtextfield
+     */
+    private void createComponents(double maxValue) {
         this.dialog = new JDialog();
 
-        this.cancel = new JButton("Cancel");
-        this.takeoff = new JButton("Takeoff");
-        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
+        this.cancel = new JButton(translate("Cancel"));
+        this.takeoff = new JButton(translate("Takeoff"));
+        this.value = new JFormattedTextField(StringDecoder.getNumberFormatter(maxValue));
+        this.enteredValue = new JLabel();
+        this.balanceAfterDeposit = new JLabel(StringDecoder.getNumberFormat().format(maxValue));
 
         this.dialog.setContentPane(new JPanel(new GridBagLayout()));
     }
 
-    public double getAmount() {
-        if (value.getText().isBlank()) {
-            showMessageDialog(null, "invalid amount", "currency must not be blank", ERROR_MESSAGE);
-            return 0;
-        }
+    /**
+     * The getAmount function is used to get the amount of currency that has been entered into the text field.
+     * @return A double value, which is the parsed amount from the text field
+     */
+    public double getAmount() throws InvalidInputException {
+        if (value.getText().isBlank())
+            throw new InvalidInputException("currency value is blank or has been invalid whilst entered");
 
         try {
-            return NumberFormat.getNumberInstance().parse(value.getText()).doubleValue();
+            return StringDecoder.getNumberFormat().parse(value.getText()).doubleValue();
         } catch (ParseException e) {
-            throw new RuntimeException(e);
+            Logging.LOGGER.severe("Amount text field contains invalid value: " + value);
+            throw new InvalidInputException(e);
         }
     }
 
+
+    /**
+     * The setCommittedValue function sets the text of the enteredValue and balanceAfterDeposit TextFields to
+     * a String representation of amount and after, respectively.
+     * @param amount Set the text of enteredvalue
+     * @param after Set the balance after deposit
+     */
+    public void setCommittedValue(double amount, double after) {
+        enteredValue.setText(StringDecoder.getNumberFormat().format(amount));
+        balanceAfterDeposit.setText(StringDecoder.getNumberFormat().format(after));
+    }
+
     public JButton getCancel() {
         return cancel;
     }
@@ -111,6 +162,10 @@ public class TakeoffView {
         return takeoff;
     }
 
+    public JFormattedTextField getValue() {
+        return value;
+    }
+
     public void dispose() {
         this.dialog.dispose();
     }

src/me/teridax/jcash/gui/transfer/TransferController.java

@@ -0,0 +1,111 @@
+package me.teridax.jcash.gui.transfer;
+
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.Main;
+import me.teridax.jcash.banking.accounts.Account;
+import me.teridax.jcash.banking.accounts.CurrentAccount;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
+import me.teridax.jcash.gui.InvalidInputException;
+import me.teridax.jcash.gui.Utils;
+
+import javax.swing.event.DocumentEvent;
+import javax.swing.event.DocumentListener;
+import java.text.ParseException;
+
+/**
+ * Dialog class for transferring some value from one account to another
+ */
+public class TransferController {
+
+    private final Account account;
+    private final TransferData transferData;
+    private final TransferView view;
+
+    public TransferController(Account account, BankingManagementSystem bms) {
+        this.account = account;
+
+        var overdraft = 0.0;
+        if (account instanceof CurrentAccount) {
+            overdraft += ((CurrentAccount) account).getOverdraft();
+        }
+
+        this.view = new TransferView(account.getBalance() + overdraft);
+        this.transferData = new TransferData(bms);
+        this.view.getTransfer().addActionListener(e -> transfer());
+        this.view.getCancel().addActionListener(e -> view.dispose());
+
+        // validates the users input
+        var validator = new DocumentListener() {
+            @Override
+            public void insertUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void removeUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+
+            @Override
+            public void changedUpdate(DocumentEvent documentEvent) {
+                validateInputState();
+            }
+        };
+
+        this.view.getValue().getDocument().addDocumentListener(validator);
+        this.view.getIbanTextField().getDocument().addDocumentListener(validator);
+        this.view.getBlzTextField().getDocument().addDocumentListener(validator);
+
+        this.view.showDialog();
+    }
+
+    /**
+     * Returns true if the target bank account is valid.
+     * @return  true if the target bank account is valid false otherwise
+     */
+    private boolean validateTargetAccount() {
+        if (transferData.validateBLZ(this.view.getBlz())) {
+            return transferData.validateIBAN(this.view.getBlz(), view.getIban());
+        }
+        return false;
+    }
+
+    /**
+     * Returns true if the entered value to transfer is valid.
+     * This method will also commit the valid value back to the text field.
+     * @return true if the value to transfer is valid, false otherwise
+     */
+    private boolean validateTransferValue() {
+        var balance = account.getBalance();
+        try {
+            view.getValue().commitEdit();
+            var amount = view.getAmount();
+            view.setCommittedValue(amount, balance - amount);
+            return true;
+        } catch (InvalidInputException | ParseException ex) {
+            view.setCommittedValue(0, balance);
+            return false;
+        }
+    }
+
+    private void validateInputState() {
+        var valid = validateTargetAccount() && validateTransferValue();
+        view.getTransfer().setEnabled(valid);
+    }
+
+    /**
+     * Attempts to transfer the balance from one account to another
+     * This method will close the dialog.
+     */
+    private void transfer() {
+        try {
+            var amount = view.getAmount();
+            this.account.takeoff(amount);
+            this.transferData.transferValue(amount, view.getBlz(), view.getIban());
+        } catch (IllegalArgumentException | InvalidInputException ex) {
+            Logging.LOGGER.severe("Could not transfer: " + ex.getMessage());
+            Utils.error("Reason: " + ex.getMessage());
+        }
+        this.view.dispose();
+    }
+}

src/me/teridax/jcash/gui/transfer/TransferData.java

@@ -1,6 +1,7 @@
 package me.teridax.jcash.gui.transfer;
 
-import me.teridax.jcash.banking.BankingManagementSystem;
+import me.teridax.jcash.Logging;
+import me.teridax.jcash.banking.management.BankingManagementSystem;
 import me.teridax.jcash.decode.StringDecoder;
 
 public class TransferData {
@@ -13,27 +14,64 @@ public class TransferData {
 
     /**
      * Transfers a certain amount of money to the specified account of the specified bank
-     * @param amount the amount to transfer
-     * @param blz the bank that manages the account
+     *
+     * @param amount     the amount to transfer
+     * @param blz        the bank that manages the account
      * @param ibanString the internal bank account number to transfer money to
      * @throws IllegalArgumentException if the bank or the account do not exist
      */
     public void transferValue(double amount, String blz, String ibanString) throws IllegalArgumentException {
+        // get bank to transfer to
         var bank = bms.getBank(blz);
-        if (bank.isEmpty())
+        if (bank.isEmpty()) {
+            Logging.LOGGER.warning("Bank not found: " + blz);
             throw new IllegalArgumentException("Bank not found: " + blz);
+        }
 
+        // validate iban of target account
         var iban = 0;
         try {
-             iban = StringDecoder.decodeUniqueIdentificationNumber(ibanString);
+            iban = StringDecoder.decodeUniqueIdentificationNumber(ibanString);
         } catch (Exception ex) {
+            Logging.LOGGER.warning("IBAN has invalid format: " + ibanString + " because: " + ex.getMessage());
             throw new IllegalArgumentException("IBAN has invalid format: " + ibanString);
         }
 
+        // get account to transfer value to
         var account = bank.get().getAccount(iban);
-        if (account.isEmpty())
+        if (account.isEmpty()) {
+            Logging.LOGGER.warning("Account not found: " + iban);
             throw new IllegalArgumentException("Account not found: " + iban);
+        }
 
         account.get().getPrimaryAccount().deposit(amount);
     }
+
+    /**
+     * Validates the given BLZ. If no bank with the given BLZ can be found
+     * this method returns false. Otherwise, true is returned.
+     * @param blz the BLZ to validate
+     * @return true if the BLZ is valid and false otherwise
+     */
+    public boolean validateBLZ(String blz) {
+        return bms.getBank(blz).isPresent();
+    }
+
+    /**
+     * Validates the given IBAN for the given BLZ. This method assumes the BLZ to be valid.
+     * If this is not the case, this function will throw an exception.
+     * Returns true if an account with the given IBAN was found for bank of the given BLZ.
+     * @param blz bank to search in
+     * @param ibanString account to search for
+     * @return true if the account was found false otherwise
+     */
+    public boolean validateIBAN(String blz, String ibanString) {
+        var bank = bms.getBank(blz);
+        try {
+            var iban = StringDecoder.decodeUniqueIdentificationNumber(ibanString);
+            return bank.map(value -> value.getAccount(iban).isPresent()).orElse(false);
+        } catch (Exception e) {
+            return false;
+        }
+    }
 }

src/me/teridax/jcash/gui/transfer/TransferDialog.java

@@ -1,31 +0,0 @@
-package me.teridax.jcash.gui.transfer;
-
-import me.teridax.jcash.banking.Account;
-import me.teridax.jcash.banking.BankingManagementSystem;
-
-import javax.swing.*;
-
-import static javax.swing.JOptionPane.ERROR_MESSAGE;
-import static javax.swing.JOptionPane.showMessageDialog;
-
-public class TransferDialog {
-
-    public TransferDialog(Account account, BankingManagementSystem bms, Runnable onDeposit) {
-        var view = new TransferView();
-        var data = new TransferData(bms);
-        view.getTransfer().addActionListener(e -> {
-            try {
-                var amount = view.getAmount();
-
-                data.transferValue(amount, view.getBlz(), view.getIban());
-                account.takeoff(amount);
-                onDeposit.run();
-                view.dispose();
-            } catch (IllegalArgumentException ex) {
-                showMessageDialog(null, "invalid account", "Could not transfer", ERROR_MESSAGE);
-            }
-        });
-        view.getCancel().addActionListener(e -> view.dispose());
-        view.showDialog();
-    }
-}

src/me/teridax/jcash/gui/transfer/TransferView.java

@@ -1,15 +1,34 @@
 package me.teridax.jcash.gui.transfer;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
+import me.teridax.jcash.gui.IconProvider;
+import me.teridax.jcash.gui.InvalidInputException;
 
 import javax.swing.*;
 import java.awt.*;
-import java.text.NumberFormat;
 import java.text.ParseException;
 
-import static javax.swing.JOptionPane.ERROR_MESSAGE;
-import static javax.swing.JOptionPane.showMessageDialog;
+import static me.teridax.jcash.lang.Translator.translate;
 
+/**
+ * JDialog for displaying the GUI for a transfer dialog
+ * with the following crude layout:
+ * <pre>
+ ┌───────────────────────────────────────────────┐
+ │       ┌─────────────┐      ┌────────────────┐ │
+ │   BLZ │             │ IBAN │                │ │
+ │       └─────────────┘      └────────────────┘ │
+ │                                               │
+ │       ┌─────────────┐                         │
+ │ VALUE │             │                         │
+ │       └─────────────┘                         │
+ │                          ┌───────┐ ┌────────┐ │
+ │                          │Cancel │ │Transfer│ │
+ │                          └───────┘ └────────┘ │
+ └───────────────────────────────────────────────┘
+ * </pre>
+ */
 public class TransferView {
 
     private JDialog dialog;
@@ -18,15 +37,21 @@ public class TransferView {
     private JFormattedTextField iban;
     private JFormattedTextField blz;
     private JFormattedTextField value;
+    private JLabel balanceAfterTransfer;
+    private JLabel enteredValue;
 
-    public TransferView() {
-        createComponents();
+    public TransferView(double maxValue) {
+        createComponents(maxValue);
         layoutComponents();
     }
 
+    /**
+     * Makes this dialog visible to the user
+     */
     public void showDialog() {
+        dialog.setIconImage(IconProvider.getWindowIcon());
         dialog.setModalityType(Dialog.ModalityType.APPLICATION_MODAL);
-        dialog.setTitle("Transfer money");
+        dialog.setTitle(translate("Transfer money"));
         dialog.pack();
         dialog.setSize(dialog.getWidth() * 2, dialog.getHeight());
         dialog.setResizable(false);
@@ -35,100 +60,142 @@ public class TransferView {
         dialog.setVisible(true);
     }
 
+    /**
+     * Layout all components of this dialog.
+     */
     private void layoutComponents() {
         var c = new GridBagConstraints();
 
         c.gridx = 0;
         c.gridy = 0;
-        c.weightx = 1;
-        c.weighty = 1;
-        c.gridwidth = 3;
-        c.fill = GridBagConstraints.HORIZONTAL;
-        c.anchor = GridBagConstraints.CENTER;
-        c.insets = new Insets(4, 4, 4, 4);
-        dialog.getContentPane().add(new JLabel("Transfer money"), c);
-
-        c.gridx = 0;
-        c.gridy = 1;
         c.gridwidth = 1;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0;
-        dialog.getContentPane().add(new JLabel("BLZ", SwingConstants.RIGHT), c);
+        c.insets = new Insets(6,6,6,6);
+        dialog.getContentPane().add(new JLabel(translate("BLZ"), SwingConstants.RIGHT), c);
 
         c.gridx = 1;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0.5;
         dialog.getContentPane().add(blz, c);
 
         c.gridx = 2;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0;
-        dialog.getContentPane().add(new JLabel("IBAN", SwingConstants.RIGHT), c);
+        dialog.getContentPane().add(new JLabel(translate("IBAN"), SwingConstants.RIGHT), c);
 
         c.gridx = 3;
-        c.gridy = 1;
+        c.gridy = 0;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 1;
         dialog.getContentPane().add(iban, c);
 
         c.gridx = 0;
-        c.gridy = 2;
+        c.gridy = 1;
         c.fill = GridBagConstraints.NONE;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0;
-        dialog.getContentPane().add(new JLabel("Betrag", SwingConstants.RIGHT), c);
+        dialog.getContentPane().add(new JLabel(translate("Betrag"), SwingConstants.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 1;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        c.weightx = 0.5;
+        dialog.getContentPane().add(value, c);
+
+        c.gridx = 0;
+        c.gridy = 2;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        c.weightx = 0.5;
+        dialog.getContentPane().add(new JLabel(translate("Value to transfer:"), JLabel.RIGHT), c);
 
         c.gridx = 1;
         c.gridy = 2;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
         c.weightx = 0.5;
-        dialog.getContentPane().add(value, c);
+        dialog.getContentPane().add(enteredValue, c);
+
+        c.gridx = 0;
+        c.gridy = 3;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        c.weightx = 0.5;
+        dialog.getContentPane().add(new JLabel(translate("Balance after transfer:"), JLabel.RIGHT), c);
+
+        c.gridx = 1;
+        c.gridy = 3;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        c.anchor = GridBagConstraints.LAST_LINE_END;
+        c.weightx = 0.5;
+        dialog.getContentPane().add(balanceAfterTransfer, c);
 
         var buttonPanel = new JPanel(new FlowLayout(FlowLayout.TRAILING));
         buttonPanel.add(cancel);
         buttonPanel.add(transfer);
 
         c.gridx = 0;
-        c.gridy = 3;
+        c.gridy = 4;
         c.gridwidth = 4;
         c.fill = GridBagConstraints.HORIZONTAL;
         c.anchor = GridBagConstraints.LAST_LINE_END;
-        c.insets = new Insets(10, 10, 10, 10);
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents() {
+    private void createComponents(double maxValue) {
         this.dialog = new JDialog();
 
-        this.cancel = new JButton("Cancel");
-        this.transfer = new JButton("Transfer");
-        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
+        this.cancel = new JButton(translate("Cancel"));
+        this.transfer = new JButton(translate("Transfer"));
+        this.transfer.setEnabled(false);
+        this.value = new JFormattedTextField(StringDecoder.getNumberFormatter(maxValue));
         this.iban = new JFormattedTextField();
         this.blz = new JFormattedTextField();
+        this.enteredValue = new JLabel();
+        this.balanceAfterTransfer = new JLabel(StringDecoder.getNumberFormat().format(maxValue));
 
         this.dialog.setContentPane(new JPanel(new GridBagLayout()));
     }
 
-    public double getAmount() {
-        if (value.getText().isBlank()) {
-            showMessageDialog(null, "invalid amount", "currency must not be blank", ERROR_MESSAGE);
-            return 0;
-        }
+    /**
+     * Returns the entered amount parsed into a double value.
+     * @return the amount parsed into a double
+     * @throws InvalidInputException if the text in {@link #value} is not a valid double value.
+     */
+    public double getAmount() throws InvalidInputException {
+        if (value.getText().isBlank())
+            throw new InvalidInputException("currency value is blank or has been invalid whilst entered");
 
         try {
-            return NumberFormat.getNumberInstance().parse(value.getText()).doubleValue();
+            return StringDecoder.getNumberFormat().parse(value.getText()).doubleValue();
         } catch (ParseException e) {
-            throw new RuntimeException(e);
+            Logging.LOGGER.severe("Amount text field contains invalid value: " + value);
+            throw new InvalidInputException(e);
         }
     }
 
+    /**
+     * Sets the values to display in the dialog labels as overview information.
+     * @param amount the amount to transfer
+     * @param after balance after the transfer
+     */
+    public void setCommittedValue(double amount, double after) {
+        enteredValue.setText(StringDecoder.getNumberFormat().format(amount));
+        balanceAfterTransfer.setText(StringDecoder.getNumberFormat().format(after));
+    }
+
+    public JFormattedTextField getValue() {
+        return value;
+    }
+
     public JButton getCancel() {
         return cancel;
     }
@@ -145,6 +212,14 @@ public class TransferView {
         return blz.getText();
     }
 
+    public JFormattedTextField getIbanTextField() {
+        return iban;
+    }
+
+    public JFormattedTextField getBlzTextField() {
+        return blz;
+    }
+
     public void dispose() {
         this.dialog.dispose();
     }

src/me/teridax/jcash/lang/Locales.java

@@ -0,0 +1,60 @@
+package me.teridax.jcash.lang;
+
+import me.teridax.jcash.Logging;
+
+import java.util.Locale;
+
+/**
+ * Class for storing static information about the locale used by the application instance at runtime.
+ */
+@SuppressWarnings("unused")
+public class Locales {
+
+    /**
+     * Default locale initialized to the fallback locale used by this application.
+     */
+    private static Locale defaultLocale = new Locale("en", "EN");
+
+    /**
+     * Sets the default locale to use for the application instance.
+     * This will instruct the translator to use the default locale as well as
+     * Java swing components.
+     *
+     * @param language the locale to use for language
+     * @param country  the locale to use for country
+     */
+    public static void setDefaultLocale(String language, String country) {
+        var locale = language + "_" + country;
+
+        if (Translator.setTranslationLocale(locale)) {
+            defaultLocale = new Locale(language, country);
+            // apply locale to JVM
+            Locale.setDefault(defaultLocale);
+        }
+        Logging.LOGGER.info("Using locale: " + locale);
+    }
+
+    public static Locale getDefaultLocale() {
+        return defaultLocale;
+    }
+
+    /**
+     * Tries to automatically detect the default locale.
+     * This will prefer the users locale over the systems locale.
+     * If both fail, the JVMs default locale will be used.
+     */
+    public static void autodetectDefaultLocale() {
+        var country = System.getProperty("user.country");
+        var language = System.getProperty("user.language");
+
+        var jvmLocale = Locale.getDefault();
+
+        if (null == country)
+            country = jvmLocale.getCountry();
+
+        if (null == language)
+            language = jvmLocale.getLanguage();
+
+        setDefaultLocale(language, country);
+    }
+}

src/me/teridax/jcash/lang/Translator.java

@@ -0,0 +1,130 @@
+package me.teridax.jcash.lang;
+
+import me.teridax.jcash.Logging;
+
+import java.nio.charset.StandardCharsets;
+import java.util.*;
+import java.util.stream.Collectors;
+
+/**
+ * Static translator class.
+ * This is a very simple translator able to translate base tokens from english into a variety of
+ * configured languages.
+ */
+public final class Translator {
+
+    /**
+     * List of all supported locales in the format: language_country. Examples: en_EN, fr_FR
+     * The index inside the list is directly related to the index of the translation array inside the list translations.
+     */
+    private static final List<String> languages = new ArrayList<>();
+    /**
+     * Mapping of a default english phrase of the code en_EN which is associated with  a list of possible translations.
+     * Index 0 of the translation is equivalent to the key itself since locale 0 is always en_EN.
+     */
+    private static final Map<String, String[]> translations = new HashMap<>();
+    /**
+     * Precomputed index of the locale used to statically translate a phrase
+     */
+    private static int localeTranslationIndex = 0;
+
+    static {
+        // read language file and parse
+        try (var stream = Objects.requireNonNull(Translator.class.getResourceAsStream("languages.csv"))) {
+            var text = new String(stream.readAllBytes(), StandardCharsets.UTF_8);
+
+            // parse each line
+            text.lines().forEach(line -> {
+                // read header i.e. the locales identifier
+                if (languages.isEmpty()) {
+                    // split string into columns by comma and trim each column
+                    languages.addAll(Arrays.stream(line.split(",")).map(String::trim).collect(Collectors.toList()));
+
+                    // check if default locale is present
+                    if (!languages.contains("en_EN")) {
+                        Logging.LOGGER.severe("Missing default en_EN locale");
+                        throw new IllegalArgumentException("Missing en_EN locale");
+                    }
+
+                    Logging.LOGGER.info("Read locales: " + Arrays.deepToString(languages.toArray()));
+                    return;
+                }
+
+                var translation = Arrays.stream(line.split(",")).map(String::trim).toArray(String[]::new);
+
+                // check if all translations are present
+                // it may happen at a locale does not provide a translation
+                if (translation.length != languages.size())
+                    Logging.LOGGER.warning("invalid translations: " + translation.length + " " + languages.size());
+
+                translations.put(translation[0], translation);
+            });
+
+        } catch (Exception e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    /**
+     * Translates the given phrase into the corresponding phrase of the selected locale of the translator.
+     * If no translation is found or no locale is defined for the translator this function will return the given phrase.
+     *
+     * @param phrase the text to translate
+     * @return the translated phrase, or the phrase itself in case no translation can be found
+     */
+    public static String translate(String phrase) {
+        try {
+            return translations.get(phrase)[localeTranslationIndex];
+
+        } catch (ArrayIndexOutOfBoundsException e) {
+            Logging.LOGGER.severe("Locale does not exist with index: " + localeTranslationIndex);
+        } catch (NullPointerException e) {
+            Logging.LOGGER.severe("No translation found for phrase: " + phrase);
+        }
+        return phrase;
+    }
+
+    /**
+     * Returns an array of all available locales for this translator
+     *
+     * @return an array of all available locales for this translator
+     */
+    public static String[] availableLocales() {
+        return languages.toArray(String[]::new);
+    }
+
+    /**
+     * Map the given locale string to an index indicating which array location to choose when fetching a result from
+     * the translation map.
+     *
+     * @param locale the locale string
+     * @return a matching index of the locale
+     * @throws IllegalArgumentException if the given locale is not part of the available locales
+     */
+    private static int mapLocaleToIndex(String locale) throws IllegalArgumentException {
+        for (int i = 0; i < languages.size(); i++) {
+            if (languages.get(i).equals(locale)) {
+                return i;
+            }
+        }
+
+        throw new IllegalArgumentException("Locale does not exist: " + locale);
+    }
+
+    /**
+     * Sets the default locale to use when translating.
+     * The locale must have the format language_COUNTRY like en_EN
+     *
+     * @param locale the locale to use when translating
+     * @return if the specified locale can be used by the translator
+     */
+    public static boolean setTranslationLocale(String locale) {
+        try {
+            localeTranslationIndex = Translator.mapLocaleToIndex(locale);
+            return true;
+        } catch (IllegalArgumentException ex) {
+            Logging.LOGGER.severe("unable to set locale for translation: " + locale + " because: " + ex.getMessage());
+            return false;
+        }
+    }
+}

src/me/teridax/jcash/lang/TranslatorTest.java

@@ -0,0 +1,41 @@
+package me.teridax.jcash.lang;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static junit.framework.TestCase.assertEquals;
+import static junit.framework.TestCase.assertTrue;
+
+public class TranslatorTest {
+
+    @Test
+    public void testLoading() {
+        // test if all locales are read
+        assertTrue(Arrays.deepEquals(Translator.availableLocales(), new String[]{"en_EN", "de_DE", "es_ES", "fr_FR", "zh_Hans"}));
+    }
+
+    @Test
+    public void testTranslationBasic() {
+        // test if basic translation works
+        Translator.setTranslationLocale("de_DE");
+        assertEquals(Translator.translate("Overdraft"), "Überziehungsbetrag");
+        assertEquals(Translator.translate("Load database"), "Datenbank auswählen");
+        assertEquals(Translator.translate("currency must not be blank"), "Betrag darf nicht leer sein");
+        assertEquals(Translator.translate("Deposit money"), "Geld einzahlen");
+
+        Translator.setTranslationLocale("es_ES");
+        assertEquals(Translator.translate("Account"), "Cuenta");
+        assertEquals(Translator.translate("Faulty login attempt"), "Solicitud de autenticación no válida");
+        assertEquals(Translator.translate("Transfer money"), "Transferencia de dinero");
+
+        // test if translation with no available translation works as expected
+        assertEquals(Translator.translate("Guppi guppi guppi"), "Guppi guppi guppi");
+    }
+
+    @Test
+    public void testInvalidLocales() {
+        // test if app crashes when invalid locale is loaded
+        Translator.setTranslationLocale("ar_TD");
+    }
+}

src/me/teridax/jcash/lang/languages.csv

@@ -0,0 +1,54 @@
+en_EN,de_DE,es_ES,fr_FR,zh_Hans
+Bank,Bank,Banco,Banque,银行
+BLZ,BLZ,BLZ,BLZ,BLZ
+PIN,PIN,PIN,PIN,密码
+Balance,Kontostand,Saldo,Solde,余额
+Account type,Kontoart,Tipo de cuenta,Type de compte,账户类型
+Interest,Zinsen,Interés,Intérêts,利息
+Overdraft,Überziehungskredit,Descubierto,Découvert,透支
+Customer number,Kundennummer,Número de cliente,Numéro de client,客户编号
+Name,Name,Nombre,Nom du client,姓名
+Name,Name,Nombre,Nom et prénom,姓名
+Street,Straße,Calle,Rue,街道
+PLZ,PLZ,PLZ,PLZ,PLZ
+City,Ort,Ciudad,Ville,城市
+Password,Kennwort,Contraseña,Mot de passe,密码
+Login,Anmeldung,Inicio de sesión,Connexion,登录
+CurrentAccount,Girokonto,Cuenta corriente,Compte courant,活期账户
+SavingsAccount,Sparkonto,CuentaAhorro,Compte d'épargne,储蓄账户
+Address,Adresse,Dirección,Adresse,地址
+Logout,Abmelden,Cerrar sesión,Déconnexion,注销
+Transfer,Überweisung,Transferir,Virement,转账
+Deposit,Einzahlen,Ingresar,Dépôt,存款
+Take off,Abheben,Retirar,Enlever,取款
+Value,Wert,Valor,Valeur,价值
+Cancel,Abbrechen,Cancelar,Annuler,取消
+Load database,Datenbank laden,Cargar base de datos,Charger la base de données,加载数据库
+Invalid account,Ungültiges Konto,Cuenta no válida,Compte non valide,无效账户
+Could not transfer,Konnte nicht übertragen werden,No se ha podido transferir,Impossible de transférer,无法转账
+Transfer,Überweisung,Transferencia,Transférer,转账
+invalid amount,Ungültiger Betrag,Importe no válido,montant non valide,无效金额
+currency must not be blank,Währung darf nicht leer sein,La divisa no debe estar en blanco,la devise ne doit pas être vide,货币不得为空
+Transfer money,Geld überweisen,Transferencia de dinero,Transférer de l'argent,转账金额
+Could not take off money,Konnte Geld nicht abheben,No se ha podido retirar el dinero,Impossible de retirer de l'argent,无法取款
+Takeoff money,Geld abheben,Retirar dinero,Retirer de l'argent,取款
+Takeoff,Abheben,Despegue,Décoller,起飞
+Currency must not be blank,Die Währung darf nicht leer sein,La divisa no debe estar en blanco,La monnaie ne doit pas être en blanc,货币不得为空
+Cashmachine,Geldautomat,Cajero,Cashmachine,提款机
+Invalid IBAN,Ungültige IBAN,IBAN no válido,IBAN non valide,IBAN 无效
+Faulty login attempt,Fehlerhafter Anmeldeversuch,Intento de acceso erróneo,Tentative de connexion erronée,尝试登录失败
+Invalid PIN,Ungültige PIN,PIN no válido,PIN invalide,密码无效
+Invalid login credentials,Ungültige Anmeldedaten,Credenciales de inicio de sesión no válidas,Identifiants de connexion invalides,登录凭证无效
+Deposit money,Geld einzahlen,Depositar dinero,Dépôt d'argent,存款
+Interest rate,Zinssatz,Tipo de interés,Taux d'intérêt,利率
+Name/Family-name,Name/Familienname,Nombre y apellidos,Nom/Prénom de famille,姓名
+Address,Anschrift,Dirección,Adresse,地址
+Account,Konto,Cuenta,Compte,账户
+Closing JCash,JCash wird geschlossen,Cerrar JCash,Clôture de JCash,关闭 JCash
+you're logged out,Sie sind abgemeldet,has cerrado sesión,Vous êtes déconnecté,您已退出登录
+Comma separated value spreadsheet,Kommagetrennte Werte-Tabelle,Hoja de cálculo de valores separados por comas,Tableur de valeurs séparées par des virgules,逗号分隔值电子表格
+Value to transfer:,Zu übertragender Wert:,Valor a transferir:,Valeur à transférer :,要转账的金额：
+Balance after transfer:,Kontostand nach Überweisung:,Saldo después de la transferencia:,Solde après transfert :,转账后的余额
+Balance after takeoff:,Kontostand nach dem Abheben:,Saldo después de retirar:,Solde après décollage :,取出后的余额
+Value to deposit:,Einzuzahlender Wert:,Valor a ingresar:,Valeur à déposer :,存款价值
+Value to takeoff:,Auszuhalender Wert:,Valor a despegar:,Valeur à l'enlèvement :,起飞价值