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How to implement an action listener using method reference in Java?
In Java 8, lambda expression accepts an anonymous function as a parameter. In the case of providing an anonymous method, we can also pass references of existing methods using "::" symbol. A method reference enables us to do the same thing but with existing methods.
We can also implement an action listener for a JButton by using static method reference and referred using the class name.
Syntax
<Class-name>:: Method-name;
Example
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class MethodReferenceButtonListenerTest extends JFrame {
private JButton button;
public MethodReferenceButtonListenerTest() {
setTitle("Method Reference Button Listener");
button = new JButton("Method Reference");
button.setBorder(BorderFactory.createLineBorder(Color.black));
button.addActionListener(MethodReferenceButtonListenerTest :: executeMethod); // static method reference
getContentPane().add(button, BorderLayout.NORTH);
setSize(400, 300);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setLocationRelativeTo(null);
setVisible(true);
}
public static void main(String args[]) throws Exception {
new MethodReferenceButtonListenerTest();
}
public static void executeMethod(ActionEvent e) {
JOptionPane.showMessageDialog(null, ((JButton)e.getSource()).getText());
}
}Output
Updated on: 11-Jul-2020
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