Why does it not work? (send function as parameter by Runnable in java )

Question

I have a project in java, and I have a problem.

Description of goal:

In Form A (MainForm) I have some buttons in enable(false) mode. I have a function LockOrUnlockButtons() that checks some conditions and if this function return true then the buttons make enable(true) state . I want to call this function for "event of the closing of Form B" (AddCstmrForm).

I tried to solve this goal with receiving this function as parameter:

public Void AddCstmrForm(Runnable myFunc) {
    .....
    ....
    }

The problem:

But in Form A (MainForm), when I send the function LockOrUnlockButtons() to the Constructor of Form B (AddCstmrForm) i got Error:

Constructor AddCstmrForm in class AddCstmrForm cannot be applied to given types.
  required: no arguments.
  founf: Void

What did I do wrong?

Harel

THE CODE: in the Form A ,(MainForm):

private void buttonAddNewCstmrCrdActionPerformed(java.awt.event.ActionEvent evt) {                                                     
         AddCstmrForm addCstmr = null;
        try 
        {
            addCstmr = new  AddCstmrForm(LockOrUnlockButtons());
        }
        catch (Exception ex) 
        {
            Logger.getLogger(MainForm.class.getName()).log(Level.SEVERE, null, ex);
        }
            addCstmr.show();
}

   private Void LockOrUnlockButtons() throws Exception
    {
         if(sngltn.GetAllCustemers().size()==0) 
            buttonUpdateAddActivityCstmrCrd.setEnabled(false);
         else
              buttonUpdateAddActivityCstmrCrd.setEnabled(true);

         if(sngltn.GetAllCustemers().size()==0) 
            buttonDeleteCstmrCrd.setEnabled(false);
         else
            buttonDeleteCstmrCrd.setEnabled(true);

         if(sngltn.GetAllCustemers().size()==0) 
            buttonQueriesViewData.setEnabled(false);
         else
            buttonQueriesViewData.setEnabled(true); 
         return null;
    }

*in the Form B(AddCstmrForm): *

public class AddCstmrForm extends javax.swing.JFrame {
    ...............
    .............
    .........
    private Runnable MainFormLockOrUnlockButton;
    ........
    public Void AddCstmrForm(Runnable myFunc) throws Exception {
    initComponents();
    ..............
    ..........
    ......
    this.MainFormLockOrUnlockButton = myFunc;
    return null;
    }
    ..............
    ..........
    ......
}

Answer 1

This isn't a constructor:

public Void AddCstmrForm(Runnable myFunc) throws Exception {
    initComponents();
    ...
}

It's a method called AddCstmrForm with a Void return type.

I think you meant:

public AddCstmrForm(Runnable myFunc) throws Exception {
    initComponents();
    ...
}

You also need to create a Runnable to call your LockOrUnlockButtons method. For example:

AddCstmrForm addCstmr = new AddCstmrForm(new Runnable() {
    @Override public void run() {
        LockOrUnlockButtons();
    }
});

Unless you're using Java 8, in which case you could write:

AddCstmrForm addCstmr = new AddCstmrForm(this::LockOrUnlockButtons);

Additionally, your LockOrUnlockButtons can be simplified significantly:

private void LockOrUnlockButtons() throws Exception {
    boolean anyCustomers = !sngltn.GetAllCustemers().isEmpty();
    buttonUpdateAddActivityCstmrCrd.setEnabled(anyCustomers);
    buttonDeleteCstmrCrd.setEnabled(anyCustomers);
    buttonQueriesViewData.setEnabled(anyCustomers);
}

(I'd also strongly advise you to follow Java naming conventions, use a return type of void rather than Void unless you really need to, and avoid throws Exception. You should revisit your exception handling approach in general, by the looks of things.)