Question

I have a Swing application in which I have multiple windows with different goals but they all have 2 things in common:

• They use a specific object which is business logic related
• They have to update some widgets with the specific object’s stuff

So, in order to avoid redundancy of code, I wanted to share some of those routines.
Maybe an example can be more clear:

public class WindowA {
     private JLabel labelA;
     // ...
     private void updateLabelInACertainManner() {
          labelA.setText(this.specificObject.getText());
     }
}

public class WindowB {
     private JLabel labelB;
     // ...
     private void updateLabelInACertainManner() {
          labelA.setText(this.specificObject.getText());
     }
}

How can I share updateLabelInACertainManner(), knowing that specificObject references the same object in both classes ?

I was thinking about inheriting both WindowA and WindowB from a WindowRoot which contains the method but how to do so having labelA and labelB are not the same object, not necessarily created in same way?

Answer 1

You could pass the label whose text should be changed as a parameter to the method in the superclass:

public class SuperWindow {
    protected void updateLabel(JLabel label) {
       label.setText("foo");
    }
}

public class WindowA extends SuperWindow {
    private JLabel labelA;
    //...

    private void somethingHappened() {
      updateLabel(labelA);
    }
}

Or you could write a getter for the label in the specific subclasses:

public class SuperWindow {
   protected abstract JLabel getLabel();

   protected void updateLabel() {
     getLabel().setText("foo");
   }
}

public class WindowA extends SuperWindow {
   private JLabel labelA;
   //...

   @Override
   protected JLabel getLabel() {
      return labelA;
   }

   private void somethingHappened() {
      updateLabel();
   }
}

And the same for specificObject.