More GUI and the Visual Editor - Beginning Java with WebSphere - page 105

3. Save the ExitButton source code.

To add the ExitButton to UsefulFrame (i.e., to relate them through composition), we must create an ExitButton
object in UsefulFrame and then add it to UsefulFrame.

4. Add the following statement immediately after the UsefulFrame class header:

private ExitButton eb= new ExitButton();

This creates an ExitButton class variable called eb and assigns an ExitButton object to eb.

5. Add the following statement to the constructor, then format, and save the source code.

this .add(eb);

This statement adds the ExitButton object to UsefulFrame. The UsefulFrame executable source code should look
like the following:

package c4;

import java.awt.Frame;
import java.awt.event.WindowListener;
import java.awt.event.WindowEvent;

public class UsefulFrame extends Frame implements WindowListener {
private ExitButton eb= new ExitButton();
public UsefulFrame () {
this .setBounds(350, 200, 400, 400);
this .setLayout( null );
this .addWindowListener( this );
this .add(eb);
}

public void windowClosing(WindowEvent e) {
this .dispose();
}
public void windowClosed(WindowEvent e) {}
public void windowDeiconified(WindowEvent e) {}
public void windowIconified(WindowEvent e) {}
public void windowOpened(WindowEvent e) {}
public void windowActivated(WindowEvent e) {}
public void windowDeactivated(WindowEvent e) {}
}

6. Run EmployeeApp.

The frame should look like Figure 4-2 .