Picture of the Problem

Look again at the method:

  public void actionPerformed( Action Event evt)
  {
    getContentPane().setBackground( Color.blue );
    repaint();
  }

The picture shows the present situation. Event objects from both buttons are delivered to the same method, which changes the background to blue no matter what event it receives.

We would like the ActionEvent that is delivered to actionPerformed() to say what should be done. To do this, you can associate a different command with each button using

setActionCommand(String command)

Now each button sends its command (a String) as part of the ActionEvent when it is clicked. The actionPerformed() method uses the command to see what to do.

If you don't use setActionCommand() to assign a command to a button, the command it sends will be the same as the text it displays. This is usually OK, but is awkward in large projects.