Tukukkk

I am relatively new to Java and am struggling to make the GUI work for a
simplified bank application logic. Besides the obvious Customer and Account
classes I have a BankLogic class that contains methods for all the
operations (deposit, creation of new accounts, customers etc), which in most
cases take in a persNumber parameter.
When it comes to the GUI, I have a menu with menu items for all the operations.

What I try to do for most of these items is:
- supply the persNr in a frame with text field.
- if the persNumber corresponds to an existing customer, then it's moving on
to doing the logic operation and displaying the relevant stuff. Display
comes in various types of frames that I create separate classes for.
Example of how this looks like:

public abstract class InputUI extends JFrame

{

private static final int FRAME_WIDTH = 450;

private static final int FRAME_HEIGHT = 100;



private JLabel persNrLabel;

private JTextField persNrInput;

private JButton button;



public InputUI()

{



    setSize(FRAME_WIDTH, FRAME_HEIGHT);

    setVisible(true);



    createTextField();

    createButton();

    createPanel();

    pack();

}



public void createTextField() {

    persNrLabel = new JLabel("Input personal number: ");

    final int FIELD_WIDTH = 10;

    persNrInput = new JTextField(FIELD_WIDTH);

}



public String getFieldText() {

    String x = persNrInput.getText();

    return x;

}



public void createButton() {

    class PersNoListener implements ActionListener

    {

        public void actionPerformed(ActionEvent event) {

            try

            {

                if (foundPersNr() == true)

                {

                    performAction();

                }

            } catch (Exception e)

            {

                JOptionPane.showMessageDialog(null, "Unknown error", "Message", JOptionPane.PLAIN_MESSAGE);

            }

        }

    }

    button = new JButton("OK");

    ActionListener listener = new PersNoListener();

    button.addActionListener(listener);

}



public abstract void performAction();



public boolean foundPersNr() {

    boolean found = false;

BankLogicInit referenced below is a class that only contains a BankLogic protected static variable (logic) - to get access to the data for the GUI, not sure this is the right approach.

    for (String searchPNr : BankLogicInit.logic.getAllCustomers()) 

    {

        if (searchPNr.contains(getFieldText()))

        {

            found = true;

        } else

        {

            JOptionPane.showMessageDialog(null, "Customer does not exist!", "Message", JOptionPane.PLAIN_MESSAGE);

        }

    }

    return found;

}



public void createPanel() {

    JPanel panel = new JPanel();

    panel.add(persNrLabel);

    panel.add(persNrInput);

    panel.add(button);



    add(panel);

}

}

Then extending this class for operations that require input of persNumber by overriding the performAction() method:

public class CreateSavAccUI extends InputUI

{



public void performAction()

{   

String persNoInput=super.getFieldText();

A. this doesn't work, but I need it to work - should return int:

   BankLogicInit.logic.createSavingsAccount(persNoInput);

B. providing a value for persNoInput method works properly

 BankLogicInit.logic.createSavingsAccount("9000000");

Then finally, displaying the appropriate view:

  SavingsAccUI=new SavingsAccUI();

I can't make the connection why B works but not A. What would be a good
solution to make A work with as little structural alterations as possible? If the answer is related to MVC, it's still unknown to me, so all guidance
and suggestions for structure would be highly appreciated. Much thanks in advance!