Graphical User Interfaces - Java - page 561

Problem

You want to use Java 8's lambda expressions to simplify GUI programming.

Solution

Write the lambda expression as the argument to, for example, JCompon-
ent.addActionListener() .

Discussion

The most common event method in Swing is JComponent's addActionListener() method.
Because ActionListener is a functional method, as defined in Chapter 9 , it can be used dir-
ectly with lambda expressions:

/** Demonstrate a JButton with Lambda Action Listeners */
public public class class ButtonDemo2L ButtonDemo2L extends extends JFrame {

private private static static final final long long serialVersionUID = 1L ;

public public ButtonDemo2L () {

super super ( "ButtonDemo Lambda" );

setDefaultCloseOperation ( JFrame . EXIT_ON_CLOSE );
setLayout ( new new FlowLayout ());

JButton b ;

add ( b = new new JButton ( "A button" ));

// Minimalist style
b . addActionListener ( e -> JOptionPane . showMessageDialog ( this this ,

"Thanks for pushing my first button!" ));

add ( b = new new JButton ( "Another button" ));

// Longer style, with { } around body.
b . addActionListener ( e -> {
JOptionPane . showMessageDialog ( this this ,

"Thanks for pushing my second button!" );

}

);

pack ();

}

public public static static void void main ( String [] args ) {