Changes:

- added logger
- restructured internal dialogs

src/me/teridax/jcash/Logging.java

@@ -0,0 +1,63 @@
+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.*;
+
+public final class Logging {
+
+    public static final Logger LOGGER = Logger.getLogger(Logging.class.getName());
+
+    private static final String LOG_FOLDER_NAME = "logs/";
+
+    /**
+     * 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);
+    }
+
+    private static void createConsoleLogger(Level level) {
+        var ch = new ConsoleHandler();
+        ch.setLevel(level);
+        LOGGER.addHandler(ch);
+    }
+
+    private static void createFileLogger(Level level) {
+        var now = LocalDateTime.now();
+        var dateTime = DateTimeFormatter.ISO_DATE_TIME.format(now);
+        var logFileName = LOG_FOLDER_NAME + dateTime + ".log";
+
+        initializeLogFolder();
+
+        try {
+            var fh = new FileHandler(logFileName);
+            fh.setLevel(level);
+            LOGGER.addHandler(fh);
+        } catch (IOException e) {
+            LOGGER.warning("Unable to initialize logging for file: " + logFileName);
+        }
+    }
+
+    private static void initializeLogFolder() {
+        var folderPath = Path.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

@@ -5,6 +5,13 @@ import me.teridax.jcash.gui.account.AccountController;
 import me.teridax.jcash.gui.login.LoginController;
 
 import javax.swing.*;
+import java.util.Objects;
+import java.util.logging.*;
+
+import static javax.swing.JOptionPane.ERROR_MESSAGE;
+import static javax.swing.JOptionPane.showMessageDialog;
+import static me.teridax.jcash.Logging.LOGGER;
+import static me.teridax.jcash.Logging.initializeSystemLogger;
 
 public final class Main {
 
@@ -27,6 +34,8 @@ public final class Main {
     }
 
     public static void main(String[] args) {
+        initializeSystemLogger(Level.FINE);
+
         // create main instance and show the login screen
         instance();
         getInstance().showLoginScreen();
@@ -51,6 +60,8 @@ public final class Main {
         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();
     }
 
@@ -61,6 +72,8 @@ public final class Main {
      */
     public void showLoginScreen() {
         SwingUtilities.invokeLater(() -> {
+            LOGGER.finer("showing login screen");
+
             try {
                 // select db file
                 var path = Loader.load();
@@ -69,6 +82,8 @@ public final class Main {
 
                 // when we have logged in set the account viewer as window content
                 login.addAccountSelectionListener(account -> {
+                    LOGGER.finer("account selected: " + Objects.toString(account, "null"));
+
                     var profileCont = new AccountController(account, login.getData().getBms());
                     this.window.setContentPane(profileCont.getView());
                     this.window.revalidate();
@@ -81,7 +96,8 @@ public final class Main {
                 this.window.setVisible(true);
 
             } catch (IllegalStateException e) {
-                System.out.println("no file selected. goodbye");
+                LOGGER.fine("Unable to show login mask: " + e.getMessage());
+                showMessageDialog(null, e.getMessage(), "Closing JCash", ERROR_MESSAGE);
                 System.exit(0);
             }
         });

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

@@ -1,5 +1,6 @@
 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;
@@ -107,6 +108,7 @@ public final class Bank {
                 }
             }
         }
+        Logging.LOGGER.finer("Account not found: " + iban);
         return Optional.empty();
     }
 }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.banking.accounts;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
@@ -40,6 +41,9 @@ public abstract class Account {
      */
     public static Account fromColumns(String[] columns) throws IllegalArgumentException, NullPointerException {
         Objects.requireNonNull(columns);
+        Logging.LOGGER.finer("Parsing account from columns");
+
+        Logging.LOGGER.finer("Decoding account fields");
 
         // deserialize fields
         var iban = StringDecoder.decodeUniqueIdentificationNumber(columns[0]);
@@ -50,15 +54,20 @@ 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
+            } 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);
         }
     }
@@ -110,8 +119,10 @@ public abstract class Account {
      * @throws IllegalArgumentException if amount is negative
      */
     public void deposit(double amount) throws IllegalArgumentException {
-        if (amount < 0)
+        if (amount < 0) {
+            Logging.LOGGER.severe("Cannot deposit negative amount of money: " + amount);
             throw new IllegalArgumentException("amount must be positive");
+        }
 
         this.balance += amount;
     }
@@ -128,8 +139,10 @@ public abstract class Account {
      * @throws IllegalArgumentException if amount is greater than the balance present
      */
     public void takeoff(double amount) throws IllegalArgumentException {
-        if (amount > this.balance)
+        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

@@ -1,5 +1,7 @@
 package me.teridax.jcash.banking.accounts;
 
+import me.teridax.jcash.Logging;
+
 /**
  * Immutable currency account storing only overdraft.
  * English equivalent to "Girokonto"
@@ -30,9 +32,12 @@ public final class CurrentAccount extends Account {
      */
     @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);
             this.overdraft += overflow;
             this.balance = 0;
         }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.banking.accounts;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 import java.util.Objects;
@@ -40,10 +41,12 @@ public final class Owner {
      */
     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]);

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

@@ -10,6 +10,8 @@ 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
@@ -17,6 +19,11 @@ import java.util.*;
  */
 public final class BankingManagementSystem {
 
+    /**
+     * Separator used to separate columns of CSV files
+     */
+    private static final String SEPARATOR = ";";
+
     /**
      * A set of banks
      */
@@ -64,6 +71,7 @@ public final class BankingManagementSystem {
      * @return a valid BMS
      */
     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);
@@ -71,13 +79,16 @@ public final class BankingManagementSystem {
             // 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));
@@ -90,8 +101,10 @@ 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);
                 }
@@ -100,8 +113,10 @@ public final class BankingManagementSystem {
             return bms;
 
         } catch (IOException e) {
+            LOGGER.severe("Could not read file: " + file + " due to: " + e.getMessage());
             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);
         }
     }

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

@@ -1,5 +1,6 @@
 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;
@@ -32,8 +33,10 @@ public class Profile {
     private final Account[] accounts;
 
     public Profile(Owner owner, Bank bank, Account account, Account[] accounts) {
-        if (!Arrays.asList(accounts).contains(account))
+        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;
@@ -69,5 +72,6 @@ public class Profile {
                 break;
             }
         }
+        Logging.LOGGER.warning("Account " + description + " not found in associated account list");
     }
 }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 
 import javax.swing.*;
@@ -42,6 +43,7 @@ public class Loader {
             }
         }
 
+        Logging.LOGGER.warning("no file selected");
         throw new IllegalStateException("No file selected");
     }
 }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.account;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.Main;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 import me.teridax.jcash.banking.management.Profile;
@@ -17,7 +18,10 @@ public class AccountController {
      */
     private final AccountView view;
 
+    private final Profile profile;
+
     public AccountController(Profile profile, BankingManagementSystem bms) {
+        this.profile = profile;
         this.view = new AccountView();
         this.view.setProfile(profile);
         this.data = new AccountData(bms);
@@ -26,16 +30,9 @@ public class AccountController {
     }
 
     private void createListeners(Profile profile) {
-        this.view.getAccountSelection().addActionListener(e -> {
+        this.view.getAccountSelection().addActionListener(e -> changeAccount());
-            var description = ((String) this.view.getAccountSelection().getSelectedItem());
-            profile.setPrimaryAccount(description);
-            this.view.setProfile(profile);
-        });
 
-        this.view.getLogout().addActionListener(e -> {
+        this.view.getLogout().addActionListener(e -> logout());
-            Main.getInstance().logout();
-            Main.getInstance().showLoginScreen();
-        });
 
         this.view.getDeposit().addActionListener(e -> new DepositDialog(profile.getPrimaryAccount(), () -> this.view.setProfile(profile)));
 
@@ -44,6 +41,19 @@ public class AccountController {
         this.view.getTransfer().addActionListener(e -> new TransferDialog(profile.getPrimaryAccount(), data.getBms(), () -> this.view.setProfile(profile)));
     }
 
+    private void logout() {
+        Logging.LOGGER.fine("Logging out of account");
+        Main.getInstance().logout();
+        Main.getInstance().showLoginScreen();
+    }
+
+    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() {
         return view;
     }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.account;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.accounts.CurrentAccount;
 import me.teridax.jcash.banking.accounts.SavingsAccount;
 import me.teridax.jcash.banking.management.Profile;
@@ -35,6 +36,7 @@ public class AccountView extends JPanel {
     }
 
     public void setProfile(Profile profile) {
+        Logging.LOGGER.finer("Changing profile of account view");
         var bank = profile.getBank();
         var account = profile.getPrimaryAccount();
         var owner = profile.getOwner();
@@ -49,12 +51,14 @@ public class AccountView extends JPanel {
         this.balance.setText(StringDecoder.LOCAL_NUMBER_FORMAT.format(account.getBalance()) + " €");
 
         this.type.setText(account.getClass().getSimpleName());
-        if (account instanceof CurrentAccount) {
+        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() + " %" );
+        } else {
+            Logging.LOGGER.severe("Type of new primary account cannot be determined: " + account.getClass().getName());
         }
 
         this.accountSelection.removeAllItems();

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

@@ -1,17 +1,37 @@
 package me.teridax.jcash.gui.deposit;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.accounts.Account;
 
 public class DepositDialog {
 
+    private final DepositView view;
+    private final Account account;
+    private final Runnable onDeposit;
+
     public DepositDialog(Account account, Runnable onDeposit) {
-        var view = new DepositView();
+        this.account = account;
-        view.getDeposit().addActionListener(e -> {
+        this.onDeposit = onDeposit;
-            account.deposit(view.getAmount());
+
+        this.view = new DepositView();
+
+        this.view.getDeposit().addActionListener(e -> depositMoney());
+        this.view.getCancel().addActionListener(e -> view.dispose());
+        this.view.showDialog();
+    }
+
+    private void depositMoney() {
+        var amount = view.getAmount();
+
+        Logging.LOGGER.fine("Depositing money of account: " + account.getIban() + " amount: " + amount);
+
+        try {
+            account.deposit(amount);
             onDeposit.run();
+        } catch (IllegalArgumentException ex) {
+            Logging.LOGGER.severe("Cannot deposit money of account: " + account.getIban() + " because: " + ex.getMessage());
+        } finally {
             view.dispose();
-        });
+        }
-        view.getCancel().addActionListener(e -> view.dispose());
-        view.showDialog();
     }
 }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.deposit;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 import javax.swing.*;
@@ -96,6 +97,7 @@ public class DepositView {
         try {
             return NumberFormat.getNumberInstance().parse(value.getText()).doubleValue();
         } catch (ParseException e) {
+            Logging.LOGGER.severe("Amount text field contains invalid value: " + value);
             throw new RuntimeException(e);
         }
     }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.login;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 
 import java.awt.event.ActionEvent;
@@ -31,6 +32,7 @@ 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();
         }
     }
@@ -40,6 +42,7 @@ 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();
         }
     }
@@ -48,12 +51,14 @@ public class LoginController {
         var blz = this.view.getBlz().getText();
         var iban = this.getIban();
         if (iban.isEmpty()) {
+            Logging.LOGGER.severe("IBAN is invalid: " + iban);
             showMessageDialog(null, "invalid IBAN", "Faulty login attempt", ERROR_MESSAGE);
             return;
         }
 
         var pin = this.getPin();
         if (pin.isEmpty()) {
+            Logging.LOGGER.severe("PIN is invalid: " + pin);
             showMessageDialog(null, "invalid pin", "Faulty login attempt", ERROR_MESSAGE);
             return;
         }
@@ -62,6 +67,7 @@ public class LoginController {
         if (account.isPresent()) {
             this.listener.onAccountSelected(account.get());
         } else {
+            Logging.LOGGER.severe("invalid login credentials: " + iban + " / " + pin);
             showMessageDialog(null, "invalid login credentials", "Faulty login attempt", ERROR_MESSAGE);
         }
     }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.login;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 import me.teridax.jcash.banking.management.Profile;
 
@@ -24,6 +25,7 @@ public class LoginData {
      * @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())
             return Optional.empty();

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.takeoff;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.accounts.Account;
 
 import static javax.swing.JOptionPane.ERROR_MESSAGE;
@@ -7,18 +8,29 @@ import static javax.swing.JOptionPane.showMessageDialog;
 
 public class TakeoffDialog {
 
+    private final Account account;
+    private final Runnable onTakeoff;
+    private final TakeoffView view;
+
     public TakeoffDialog(Account account, Runnable onTakeoff) {
-        var view = new TakeoffView();
+        this.account = account;
-        view.getTakeoff().addActionListener(e -> {
+        this.onTakeoff = onTakeoff;
+
+        this.view = new TakeoffView();
+
+        this.view.getTakeoff().addActionListener(e -> takeOff());
+        this.view.getCancel().addActionListener(e -> view.dispose());
+        this.view.showDialog();
+    }
+
+    private void takeOff() {
         try {
             account.takeoff(view.getAmount());
             onTakeoff.run();
             view.dispose();
         } catch (IllegalArgumentException ex) {
+            Logging.LOGGER.severe("Could not take off money: " + ex.getMessage());
             showMessageDialog(null, "Reason: " + ex.getMessage(), "Could not take off money", ERROR_MESSAGE);
         }
-        });
-        view.getCancel().addActionListener(e -> view.dispose());
-        view.showDialog();
     }
 }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.transfer;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 import me.teridax.jcash.decode.StringDecoder;
 
@@ -20,19 +21,24 @@ public class TransferData {
      */
     public void transferValue(double amount, String blz, String ibanString) throws IllegalArgumentException {
         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);
+        }
 
         var iban = 0;
         try {
              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);
         }
 
         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);
     }

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

@@ -1,5 +1,6 @@
 package me.teridax.jcash.gui.transfer;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.banking.accounts.Account;
 import me.teridax.jcash.banking.management.BankingManagementSystem;
 
@@ -8,22 +9,33 @@ import static javax.swing.JOptionPane.showMessageDialog;
 
 public class TransferDialog {
 
+    private final Account account;
+    private final Runnable onDeposit;
+    private final TransferData transferData;
+    private final TransferView transferView;
+
     public TransferDialog(Account account, BankingManagementSystem bms, Runnable onDeposit) {
-        var view = new TransferView();
+        this.account = account;
-        var data = new TransferData(bms);
+        this.onDeposit = onDeposit;
-        view.getTransfer().addActionListener(e -> {
+
+        transferView = new TransferView();
+        transferData = new TransferData(bms);
+        transferView.getTransfer().addActionListener(e -> transfer());
+        transferView.getCancel().addActionListener(e -> transferView.dispose());
+        transferView.showDialog();
+    }
+
+    private void transfer() {
         try {
-                var amount = view.getAmount();
+            var amount = transferView.getAmount();
 
             account.takeoff(amount);
-                data.transferValue(amount, view.getBlz(), view.getIban());
+            transferData.transferValue(amount, transferView.getBlz(), transferView.getIban());
             onDeposit.run();
-                view.dispose();
+            transferView.dispose();
         } catch (IllegalArgumentException ex) {
+            Logging.LOGGER.severe("Could not transfer: " + ex.getMessage());
             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

@@ -1,11 +1,10 @@
 package me.teridax.jcash.gui.transfer;
 
+import me.teridax.jcash.Logging;
 import me.teridax.jcash.decode.StringDecoder;
 
 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;
@@ -118,13 +117,15 @@ public class TransferView {
 
     public double getAmount() {
         if (value.getText().isBlank()) {
+            Logging.LOGGER.severe("Amount is empty");
             showMessageDialog(null, "invalid amount", "currency must not be blank", ERROR_MESSAGE);
             return 0;
         }
 
         try {
-            return NumberFormat.getNumberInstance().parse(value.getText()).doubleValue();
+            return StringDecoder.decodeCurrency(value.getText());
-        } catch (ParseException e) {
+        } catch (IllegalArgumentException e) {
+            Logging.LOGGER.severe("Invalid amount: " + value.getText());
             throw new RuntimeException(e);
         }
     }