More Blanks to Fill

Add some logic so that a different action is performed for each button. An ActionEvent object contains its button's command. To get it, use the getActionCommand() method. For example, if evt refers to an ActionEvent, then evt.getActionCommand() returns the command.

Since the command is a string, use equals( String ) to compare the command to another string.

public class TwoButtons extends JFrame implements ActionListener
{
  JButton redButton ;
  JButton grnButton ;

  // constructor for TwoButtons
  public TwoButtons()                           
  {
    redButton = new JButton("Red");
    grnButton = new JButton("Green");
    getContentPane().setLayout( new FlowLayout() ); 
    getContentPane().add( redButton );                      
    getContentPane().add( grnButton );
    
    // register the buttonDemo frame
    // (the frame this constructor is making)
    // as the listener for both Buttons.
     
    redButton.addActionListener( this );
    grnButton.addActionListener( this );
    
     redButton.setActionCommand( "red" );    
     grnButton.setActionCommand( "green" );    
  }


  public void actionPerformed( ActionEvent evt)
  {
    if ( evt.getActionCommand().equals( ________ ) )
      getContentPane().setBackground( ____________ );    
    else 
      getContentPane().setBackground( Color.green );    

    repaint(); 
  }
  . . . . . . . .
}