added javadoc and implemented transfer functionality

src/me/teridax/jcash/Main.java

@@ -65,7 +65,7 @@ public final class Main {
 
                 // when we have logged in set the account viewer as window content
                 login.addAccountSelectionListener(account -> {
-                    var profileCont = new AccountController(account);
+                    var profileCont = new AccountController(account, login.getData().getBms());
                     this.window.setContentPane(profileCont.getView());
                     this.window.revalidate();
                     this.window.repaint();
@@ -78,6 +78,7 @@ public final class Main {
 
             } catch (IllegalStateException e) {
                 System.out.println("no file selected. goodbye");
+                System.exit(0);
             }
         });
     }

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

@@ -1,14 +1,27 @@
 package me.teridax.jcash.banking;
 
-import me.teridax.jcash.decode.StringUtils;
+import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
 
+/**
+ * Base class for bank accounts.
+ * Stores the iban, pin and balance.
+ */
 @SuppressWarnings("unused")
 public abstract class Account {
 
+    /**
+     * International bank account number
+     */
     private final int iban;
+    /**
+     * Personal identification number
+     */
     private final int pin;
+    /**
+     * Balance of this account
+     */
     private double balance;
 
     public Account(int iban, int pin, double balance) {
@@ -17,20 +30,30 @@ public abstract class Account {
         this.balance = balance;
     }
 
-    public static Account fromColumns(String[] columns) {
+    /**
+     * 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}
+     * @throws IllegalArgumentException if the account type cannot be determined or the provided data is invalid
+     * @throws NullPointerException if columns is null
+     */
+    public static Account fromColumns(String[] columns) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(columns);
 
-        var iban = StringUtils.decodeUniqueIdentificationNumber(columns[0]);
+        // deserialize fields
-        var pin = StringUtils.decodeUniqueIdentificationNumber(columns[1]);
+        var iban = StringDecoder.decodeUniqueIdentificationNumber(columns[0]);
-        var balance = StringUtils.decodeCurrency(columns[2]);
+        var pin = StringDecoder.decodeUniqueIdentificationNumber(columns[1]);
-        var type = StringUtils.decodeName(columns[3]);
+        var balance = StringDecoder.decodeCurrency(columns[2]);
+        var type = StringDecoder.decodeName(columns[3]);
 
+        // try to detect the specific runtime class to deserialize
         try {
             if (type.equals("Sparkonto")) {
-                var interest = StringUtils.decodePercent(columns[4]);
+                var interest = StringDecoder.decodePercent(columns[4]);
                 return new SavingsAccount(iban, pin, balance, interest);
             } else if (type.equals("Girokonto")) {
-                var overdraft = StringUtils.decodeCurrency(columns[5]);
+                var overdraft = StringDecoder.decodeCurrency(columns[5]);
                 return new CurrentAccount(iban, pin, balance, overdraft);
             } else {
                 throw new IllegalArgumentException("Invalid account type: " + type);
@@ -65,6 +88,12 @@ public abstract class Account {
         return false;
     }
 
+    /**
+     * 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());
     }
@@ -78,6 +107,11 @@ public abstract class Account {
         return String.format("@Account [iban=%d, pin=%d, balance=%.2f]", iban, pin, balance);
     }
 
+    /**
+     * 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
+     */
     public void takeoff(double amount) {
         this.balance = Math.max(0, this.balance - amount);
     }

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

@@ -3,10 +3,24 @@ package me.teridax.jcash.banking;
 import java.util.*;
 import java.util.regex.Pattern;
 
+/**
+ * Bank storing a name, blz and a list of owners and their accounts for this bank.
+ */
 @SuppressWarnings("unused")
 public final class Bank {
+    /**
+     * The name of the bank
+     */
     private final String name;
+
+    /**
+     * Bankleitzahl. Identification number of banks in germany
+     */
     private final String blz;
+
+    /**
+     * A map of banking accounts associated with their respective owner
+     */
     private final Map<Owner, Set<Account>> accounts;
 
     Bank(String blz, String name) {
@@ -23,6 +37,13 @@ public final class Bank {
         return name;
     }
 
+    /**
+     * 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 account the account of the owner
+     */
     public void addAccount(Owner owner, Account account) {
         var set = this.accounts.getOrDefault(owner, new HashSet<>());
         set.add(account);
@@ -42,12 +63,23 @@ public final class Bank {
         return Objects.hash(blz);
     }
 
+    /**
+     * 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
+     */
     public Account[] getAccountsOfOwner(Owner owner) {
         return accounts.get(owner).toArray(Account[]::new);
     }
 
-    public static String validateBlz(String maybeBlz) {
+    /**
-        var pattern = Pattern.compile("[\\w\\d-_]+");
+     * 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())
@@ -56,11 +88,17 @@ public final class Bank {
         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
+     */
     public Optional<Profile> getAccount(int iban) {
+        // find the account which has the supplied iban
+
         for (var owner : this.accounts.entrySet()) {
             for (var account : owner.getValue()) {
-                var tmp = account.getIban();
+                if (iban == account.getIban()) {
-                if (tmp == iban) {
                     return Optional.of(new Profile(owner.getKey(), this, account, getAccountsOfOwner(owner.getKey())));
                 }
             }

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

@@ -1,42 +1,90 @@
 package me.teridax.jcash.banking;
 
-import me.teridax.jcash.decode.StringUtils;
+import me.teridax.jcash.decode.StringDecoder;
 
 import java.io.IOException;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.*;
 
+/**
+ * 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
+ * principles.
+ */
 public final class BankingManagementSystem {
 
+    /**
+     * A set of banks
+     */
     private final Set<Bank> banks;
 
     private BankingManagementSystem() {
         this.banks = new HashSet<>();
     }
 
+    /**
+     * 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
+     */
     private static String[] tail(String[] array, int index) {
         return Arrays.stream(array).skip(index).toArray(String[]::new);
     }
 
-    public static BankingManagementSystem loadFromCsv(Path file) {
+    /**
+     * Loads an instance of this class from a csv file.
+     * The csv file must comply to the formats of {@link StringDecoder} and must contain
+     * the following columns in this exact order:
+     * <ol>
+     *     <li>Bank name</li>
+     *     <li>Bank BLZ</li>
+     *     <li>Account IBAN</li>
+     *     <li>Account PIN</li>
+     *     <li>Account Balance</li>
+     *     <li>Account type</li>
+     *     <li>Account Interest rate</li>
+     *     <li>Account Overdraft</li>
+     *     <li>Owner uuid</li>
+     *     <li>Owner family name</li>
+     *     <li>Owner name</li>
+     *     <li>Owner street</li>
+     *     <li>Owner plz</li>
+     *     <li>Owner city</li>
+     * </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
+     */
+    public static BankingManagementSystem loadFromCsv(Path file) throws IllegalArgumentException {
         try {
             var bms = new BankingManagementSystem();
             var content = Files.readString(file);
 
+            // read line by line
+            // and skip the first line
             content.lines().skip(1).forEach(line -> {
+                // split the line into columns
                 var columns = line.split(";");
 
+                // one line must contain exactly 14 columns
                 if (columns.length != 14)
                     throw new IllegalArgumentException("invalid column count: " + columns.length);
 
+                // read basic fields
                 var owner = Owner.fromColumns(tail(columns, 8));
                 var account = Account.fromColumns(tail(columns, 2));
 
                 var blz = Bank.validateBlz(columns[1]);
-                var name = StringUtils.decodeName(columns[0]);
+                var name = StringDecoder.decodeName(columns[0]);
                 var bankOfLine = new Bank(blz, name);
 
+                // add banks to bms
+
                 var bankOfSet = bms.banks.stream().filter(b -> b.equals(bankOfLine)).findFirst();
                 if (bankOfSet.isPresent()) {
                     bankOfSet.get().addAccount(owner, account);
@@ -55,6 +103,11 @@ public final class BankingManagementSystem {
         }
     }
 
+    /**
+     * Return a bank with the given blz.
+     * @param blz the blz to search bank of
+     * @return the bank with this blz or none
+     */
     public Optional<Bank> getBank(String blz) {
         return this.banks.stream().filter(b -> b.getBlz().equals(blz)).findFirst();
     }

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

@@ -1,7 +1,14 @@
 package me.teridax.jcash.banking;
 
-public class CurrentAccount extends Account {
+/**
+ * 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) {

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

@@ -4,7 +4,7 @@ import org.junit.Test;
 
 import java.nio.file.Paths;
 
-public class Tests {
+public class DataClassTests {
 
     @Test
     public void test() {

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

@@ -1,17 +1,26 @@
 package me.teridax.jcash.banking;
 
-import me.teridax.jcash.decode.StringUtils;
+import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
 
+/**
+ * Represents a person owning an account.
+ */
 @SuppressWarnings("unused")
 public final class Owner {
-    private int uid;
+    /**
-    private String familyName;
+     * unique identifier
-    private String name;
+     */
-    private String street;
+    private final int uid;
-    private int zip;
+    private final String familyName;
-    private String city;
+    private final String name;
+    private final String street;
+    /**
+     * postal code
+     */
+    private final int zip;
+    private final String city;
 
     private Owner(int uid, String familyName, String name, int zip, String city, String street) {
         this.uid = uid;
@@ -22,18 +31,26 @@ public final class Owner {
         this.street = street;
     }
 
+    /**
+     * 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
+     */
     public static Owner fromColumns(String... columns) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(columns);
 
         if (columns.length != 6)
             throw new IllegalArgumentException("Invalid number of columns: " + columns.length);
 
-        var uid = StringUtils.decodeUniqueIdentificationNumber(columns[0]);
+        // decode fields
-        var familyName = StringUtils.decodeName(columns[1]);
+        var uid = StringDecoder.decodeUniqueIdentificationNumber(columns[0]);
-        var name = StringUtils.decodeName(columns[2]);
+        var familyName = StringDecoder.decodeName(columns[1]);
-        var street = StringUtils.decodeStreet(columns[3]);
+        var name = StringDecoder.decodeName(columns[2]);
-        var zip = StringUtils.decodeUniqueIdentificationNumber(columns[4]);
+        var street = StringDecoder.decodeStreet(columns[3]);
-        var city = StringUtils.decodeName(columns[5]);
+        var zip = StringDecoder.decodeUniqueIdentificationNumber(columns[4]);
+        var city = StringDecoder.decodeName(columns[5]);
 
         return new Owner(uid, familyName, name, zip, city, street);
     }

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

@@ -1,11 +1,17 @@
 package me.teridax.jcash.banking;
 
+/**
+ * Groups an owner and all of its accounts registered at a specific bank together.
+ * The profile is oriented around a primary account of the owner.
+ * This class is meant to be a read only reference for easier runtime processing of
+ * data packed into nested structure of objects.
+ */
 public class Profile {
 
-    private Owner owner;
+    private final Owner owner;
-    private Bank bank;
+    private final Bank bank;
     private Account primaryAccount;
-    private Account[] accounts;
+    private final Account[] accounts;
 
     public Profile(Owner owner, Bank bank, Account account, Account[] accounts) {
         this.owner = owner;
@@ -30,6 +36,11 @@ public class Profile {
         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)) {

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

@@ -1,8 +1,15 @@
 package me.teridax.jcash.banking;
 
+/**
+ * Savings account representing a german "Sparkonto".
+ * To the balance a certain interest rate is added.
+ */
 @SuppressWarnings("unused")
-public class SavingsAccount extends Account {
+public final class SavingsAccount extends Account {
 
+    /**
+     * interest rate applied to the balance of the super class
+     */
     private final double interest;
 
     public SavingsAccount(int iban, int pin, double balance, double interest) {

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

@@ -14,7 +14,7 @@ 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 StringUtils {
+public class StringDecoder {
 
     /**
      * Locale to use when converting strings

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

@@ -1,18 +1,26 @@
 package me.teridax.jcash.gui.account;
 
 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;
 
+/**
+ * Controller for controlling the gui of an account.
+ */
 public class AccountController {
-
+    private final AccountData data;
+    /**
+     * GUI if an account
+     */
     private final AccountView view;
 
-    public AccountController(Profile profile) {
+    public AccountController(Profile profile, BankingManagementSystem bms) {
         this.view = new AccountView();
         this.view.setProfile(profile);
+        this.data = new AccountData(bms);
 
         createListeners(profile);
     }
@@ -29,17 +37,11 @@ public class AccountController {
             Main.getInstance().showLoginScreen();
         });
 
-        this.view.getDeposit().addActionListener(e -> {
+        this.view.getDeposit().addActionListener(e -> new DepositDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile)));
-            new DepositDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile));
-        });
 
-        this.view.getTakeoff().addActionListener(e -> {
+        this.view.getTakeoff().addActionListener(e -> new TakeoffDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile)));
-            new TakeoffDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile));
-        });
 
-        this.view.getTransfer().addActionListener(e -> {
+        this.view.getTransfer().addActionListener(e -> new TransferDialog(profile.getPrimaryAccount(), data.getBms(), () -> this.view.setProfile(profile)));
-            new TransferDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile));
-        });
     }
 
     public AccountView getView() {

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

@@ -0,0 +1,16 @@
+package me.teridax.jcash.gui.account;
+
+import me.teridax.jcash.banking.BankingManagementSystem;
+
+public class AccountData {
+
+    private final BankingManagementSystem bms;
+
+    public AccountData(BankingManagementSystem bms) {
+        this.bms = bms;
+    }
+
+    public BankingManagementSystem getBms() {
+        return bms;
+    }
+}

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

@@ -1,11 +1,13 @@
 package me.teridax.jcash.gui.account;
 
 import me.teridax.jcash.banking.*;
-import me.teridax.jcash.decode.StringUtils;
+import me.teridax.jcash.decode.StringDecoder;
 
 import javax.swing.*;
 import java.awt.*;
 
+import static javax.swing.SwingConstants.RIGHT;
+
 public class AccountView extends JPanel {
 
     private JTextField iban;
@@ -16,13 +18,8 @@ public class AccountView extends JPanel {
     private JTextField type;
     private JTextField typeSpecialProperty;
     private JTextField balance;
-
     private JLabel typeSpecialLabel;
-
     private JComboBox<String> accountSelection;
-
-    private JPanel content;
-
     private JButton logout;
     private JButton transfer;
     private JButton deposit;
@@ -47,12 +44,12 @@ public class AccountView extends JPanel {
         this.name.setText(owner.getName() + " " + owner.getFamilyName());
         this.address.setText(owner.getStreet() + " " + owner.getCity());
 
-        this.balance.setText(StringUtils.LOCAL_NUMBER_FORMAT.format(account.getBalance()) + " €");
+        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( StringUtils.LOCAL_NUMBER_FORMAT.format(((CurrentAccount) account).getOverdraft()) + " €");
+            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() + " %" );
@@ -67,10 +64,11 @@ public class AccountView extends JPanel {
     }
 
     private void createLayout() {
-        setLayout(new BorderLayout(16, 16));
+        var content = new JPanel(new GridBagLayout());
-        add(new JScrollPane(content), BorderLayout.CENTER);
+
+        this.setLayout(new BorderLayout(16, 16));
+        this.add(new JScrollPane(content), BorderLayout.CENTER);
 
-        content.setLayout(new GridBagLayout());
         var constraints = new GridBagConstraints();
 
         constraints.gridwidth = 4;
@@ -80,14 +78,14 @@ public class AccountView extends JPanel {
         accountSelectionPanel.add(iban, BorderLayout.CENTER);
         accountSelectionPanel.add(accountSelection, BorderLayout.EAST);
 
-        addInputRow(constraints, content, accountSelectionPanel, 1, new JLabel("IBAN", SwingConstants.RIGHT));
+        addInputRow(constraints, content, accountSelectionPanel, 1, new JLabel("IBAN", RIGHT));
-        addInputRow(constraints, content, name, 2, new JLabel("Name/Family-name", SwingConstants.RIGHT));
+        addInputRow(constraints, content, name, 2, new JLabel("Name/Family-name", RIGHT));
-        addInputRow(constraints, content, address, 3, new JLabel("Address", SwingConstants.RIGHT));
+        addInputRow(constraints, content, address, 3, new JLabel("Address", RIGHT));
-        addInputRow(constraints, content, bankName, 4, new JLabel("Bank", SwingConstants.RIGHT));
+        addInputRow(constraints, content, bankName, 4, new JLabel("Bank", RIGHT));
-        addInputRow(constraints, content, blz, 5, new JLabel("BLZ", SwingConstants.RIGHT));
+        addInputRow(constraints, content, blz, 5, new JLabel("BLZ", RIGHT));
-        addInputRow(constraints, content, type, 6, new JLabel("Account", SwingConstants.RIGHT));
+        addInputRow(constraints, content, type, 6, new JLabel("Account", RIGHT));
         addInputRow(constraints, content, typeSpecialProperty, 7, typeSpecialLabel);
-        addInputRow(constraints, content, balance, 8, new JLabel("Balance", SwingConstants.RIGHT));
+        addInputRow(constraints, content, balance, 8, new JLabel("Balance", RIGHT));
 
         var buttonPanel = Box.createHorizontalBox();
         buttonPanel.add(Box.createHorizontalStrut(4));
@@ -121,18 +119,25 @@ public class AccountView extends JPanel {
         this.balance.setEditable(false);
         this.typeSpecialProperty.setEditable(false);
 
-        this.typeSpecialLabel = new JLabel("", SwingConstants.RIGHT);
+        this.typeSpecialLabel = new JLabel("", RIGHT);
 
         this.accountSelection = new JComboBox<>();
 
-        this.content = new JPanel();
-
         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;

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

@@ -5,7 +5,7 @@ import me.teridax.jcash.banking.Account;
 public class DepositDialog {
 
     public DepositDialog(Account account, Runnable onDeposit) {
-        var view = new DepositView(account);
+        var view = new DepositView();
         view.getDeposit().addActionListener(e -> {
             account.deposit(view.getAmount());
             onDeposit.run();

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

@@ -1,7 +1,7 @@
 package me.teridax.jcash.gui.deposit;
 
 import me.teridax.jcash.banking.Account;
-import me.teridax.jcash.decode.StringUtils;
+import me.teridax.jcash.decode.StringDecoder;
 
 import javax.swing.*;
 import java.awt.*;
@@ -15,8 +15,8 @@ public class DepositView {
     private JButton deposit;
     private JFormattedTextField value;
 
-    public DepositView(Account account) {
+    public DepositView() {
-        createComponents(account);
+        createComponents();
         layoutComponents();
     }
 
@@ -80,12 +80,12 @@ public class DepositView {
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents(Account account) {
+    private void createComponents() {
         this.dialog = new JDialog();
 
         this.cancel = new JButton("Cancel");
         this.deposit = new JButton("Deposit");
-        this.value = new JFormattedTextField(StringUtils.LOCAL_NUMBER_FORMAT);
+        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
 
         this.dialog.setContentPane(new JPanel(new GridBagLayout()));
     }

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

@@ -2,7 +2,15 @@ package me.teridax.jcash.gui.login;
 
 import me.teridax.jcash.banking.Profile;
 
+/**
+ * Listens for changes in a selected account.
+ */
 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

@@ -6,6 +6,9 @@ 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;
@@ -46,12 +49,13 @@ public class LoginController {
         var blz = this.view.getBlz().getText();
         var iban = this.getIban();
         if (iban.isEmpty()) {
-            JOptionPane.showMessageDialog(null, "invalid IBAN", "Faulty login attempt", JOptionPane.ERROR_MESSAGE);
+            showMessageDialog(null, "invalid IBAN", "Faulty login attempt", ERROR_MESSAGE);
             return;
         }
+
         var pin = this.getPin();
         if (pin.isEmpty()) {
-            JOptionPane.showMessageDialog(null, "invalid pin", "Faulty login attempt", JOptionPane.ERROR_MESSAGE);
+            showMessageDialog(null, "invalid pin", "Faulty login attempt", ERROR_MESSAGE);
             return;
         }
 
@@ -59,7 +63,7 @@ public class LoginController {
         if (account.isPresent()) {
             this.listener.onAccountSelected(account.get());
         } else {
-            JOptionPane.showMessageDialog(null, "invalid login credentials", "Faulty login attempt", JOptionPane.ERROR_MESSAGE);
+            showMessageDialog(null, "invalid login credentials", "Faulty login attempt", ERROR_MESSAGE);
         }
     }
 
@@ -70,4 +74,8 @@ public class LoginController {
     public LoginView getView() {
         return view;
     }
+
+    public LoginData getData() {
+        return data;
+    }
 }

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

@@ -5,6 +5,9 @@ import me.teridax.jcash.banking.Profile;
 
 import java.util.Optional;
 
+/**
+ * Wrapper class for a {@link me.teridax.jcash.banking.BankingManagementSystem}
+ */
 public class LoginData {
 
     private final BankingManagementSystem bms;
@@ -13,6 +16,13 @@ public class LoginData {
         this.bms = bms;
     }
 
+    /**
+     * authenticate the specified account with the provided pin.
+     * @param blz the bank identifier
+     * @param iban the account identifier
+     * @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) {
         var optionalBank = bms.getBank(blz);
         if (optionalBank.isEmpty())
@@ -21,4 +31,8 @@ public class LoginData {
         var profile = optionalBank.get().getAccount(iban);
         return profile.filter(value -> value.getPrimaryAccount().getPin() == pin);
     }
+
+    public BankingManagementSystem getBms() {
+        return bms;
+    }
 }

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

@@ -7,34 +7,32 @@ import java.text.NumberFormat;
 
 public class LoginView extends JPanel {
 
-    private final JFormattedTextField blz;
+    private JFormattedTextField blz;
-    private final JFormattedTextField iban;
+    private JFormattedTextField iban;
-    private final JPasswordField pin;
+    private JPasswordField pin;
-    private final JButton login;
+    private JButton login;
 
     public LoginView() {
-        this.blz = new JFormattedTextField("MA2424");
+        createComponents();
-        this.iban = new JFormattedTextField(getNumberFormat());
+        layoutComponents();
-        this.iban.setText("4711");
+    }
-        this.pin = new JPasswordField("1234");
+
-        this.login = new JButton("Login");
+    private void layoutComponents() {
+        var content = new JPanel(new GridBagLayout());
 
-        setLayout(new BorderLayout(16, 16));
-        var content = new JPanel();
         this.setBorder(BorderFactory.createEmptyBorder(8,8,8,8));
-        add(new JScrollPane(content), BorderLayout.CENTER);
+        this.setLayout(new BorderLayout(16, 16));
-        add(new JLabel("Bankautomat"), BorderLayout.NORTH);
+        this.add(new JScrollPane(content), BorderLayout.CENTER);
+        this.add(new JLabel("Bankautomat"), BorderLayout.NORTH);
 
-        var layout = new GridBagLayout();
         var constraints = new GridBagConstraints();
-        content.setLayout(layout);
 
         constraints.gridwidth = 4;
         constraints.insets = new Insets(12,12,12,12);
 
         addInputRow(constraints, content, blz, 1, "BLZ");
-        addInputRow(constraints, content, iban, 2, "Kontonummer");
+        addInputRow(constraints, content, iban, 2, "IBAN");
-        addInputRow(constraints, content, pin, 3, "Passwort");
+        addInputRow(constraints, content, pin, 3, "PIN");
 
         constraints.gridy = 4;
         constraints.anchor = GridBagConstraints.PAGE_END;
@@ -44,6 +42,14 @@ public class LoginView extends JPanel {
         content.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");
+    }
+
     private NumberFormatter getNumberFormat() {
         var format = NumberFormat.getIntegerInstance();
         format.setGroupingUsed(false);

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

@@ -5,7 +5,7 @@ import me.teridax.jcash.banking.Account;
 public class TakeoffDialog {
 
     public TakeoffDialog(Account account, Runnable onTakeoff) {
-        var view = new TakeoffView(account);
+        var view = new TakeoffView();
         view.getTakeoff().addActionListener(e -> {
             account.takeoff(view.getAmount());
             onTakeoff.run();

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

@@ -1,7 +1,6 @@
 package me.teridax.jcash.gui.takeoff;
 
-import me.teridax.jcash.banking.Account;
+import me.teridax.jcash.decode.StringDecoder;
-import me.teridax.jcash.decode.StringUtils;
 
 import javax.swing.*;
 import java.awt.*;
@@ -18,8 +17,8 @@ public class TakeoffView {
     private JButton takeoff;
     private JFormattedTextField value;
 
-    public TakeoffView(Account account) {
+    public TakeoffView() {
-        createComponents(account);
+        createComponents();
         layoutComponents();
     }
 
@@ -81,12 +80,12 @@ public class TakeoffView {
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents(Account account) {
+    private void createComponents() {
         this.dialog = new JDialog();
 
         this.cancel = new JButton("Cancel");
         this.takeoff = new JButton("Takeoff");
-        this.value = new JFormattedTextField(StringUtils.LOCAL_NUMBER_FORMAT);
+        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
 
         this.dialog.setContentPane(new JPanel(new GridBagLayout()));
     }

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

@@ -0,0 +1,39 @@
+package me.teridax.jcash.gui.transfer;
+
+import me.teridax.jcash.banking.BankingManagementSystem;
+import me.teridax.jcash.decode.StringDecoder;
+
+public class TransferData {
+
+    private final BankingManagementSystem bms;
+
+    public TransferData(BankingManagementSystem bms) {
+        this.bms = bms;
+    }
+
+    /**
+     * 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 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 {
+        var bank = bms.getBank(blz);
+        if (bank.isEmpty())
+            throw new IllegalArgumentException("Bank not found: " + blz);
+
+        var iban = 0;
+        try {
+             iban = StringDecoder.decodeUniqueIdentificationNumber(ibanString);
+        } catch (Exception ex) {
+            throw new IllegalArgumentException("IBAN has invalid format: " + ibanString);
+        }
+
+        var account = bank.get().getAccount(iban);
+        if (account.isEmpty())
+            throw new IllegalArgumentException("Account not found: " + iban);
+
+        account.get().getPrimaryAccount().deposit(amount);
+    }
+}

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

@@ -1,15 +1,29 @@
 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, Runnable onDeposit) {
+    public TransferDialog(Account account, BankingManagementSystem bms, Runnable onDeposit) {
-        var view = new TransferView(account);
+        var view = new TransferView();
+        var data = new TransferData(bms);
         view.getTransfer().addActionListener(e -> {
-            account.takeoff(view.getAmount());
+            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

@@ -1,7 +1,6 @@
 package me.teridax.jcash.gui.transfer;
 
-import me.teridax.jcash.banking.Account;
+import me.teridax.jcash.decode.StringDecoder;
-import me.teridax.jcash.decode.StringUtils;
 
 import javax.swing.*;
 import java.awt.*;
@@ -20,8 +19,8 @@ public class TransferView {
     private JFormattedTextField blz;
     private JFormattedTextField value;
 
-    public TransferView(Account account) {
+    public TransferView() {
-        createComponents(account);
+        createComponents();
         layoutComponents();
     }
 
@@ -105,12 +104,12 @@ public class TransferView {
         dialog.getContentPane().add(buttonPanel, c);
     }
 
-    private void createComponents(Account account) {
+    private void createComponents() {
         this.dialog = new JDialog();
 
         this.cancel = new JButton("Cancel");
         this.transfer = new JButton("Transfer");
-        this.value = new JFormattedTextField(StringUtils.LOCAL_NUMBER_FORMAT);
+        this.value = new JFormattedTextField(StringDecoder.LOCAL_NUMBER_FORMAT);
         this.iban = new JFormattedTextField();
         this.blz = new JFormattedTextField();
 
@@ -138,6 +137,14 @@ public class TransferView {
         return transfer;
     }
 
+    public String getIban() {
+        return iban.getText();
+    }
+
+    public String getBlz() {
+        return blz.getText();
+    }
+
     public void dispose() {
         this.dialog.dispose();
     }