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How to implement the listeners using lambda expressions in Java?
When we are using a lambda expression for java listener, we do not have to explicitly implement the ActionListener interface. Instead, we can use the below syntax.
Syntax
button.addActionListener(e -> { // some statements });An ActionListener interface defines only one method actionPerformed(). It is a functional interface which means that there's a place to use lambda expressions to replace the code.
Example
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class LambdaListenerTest extends JFrame {
public static void main(String args[]) {
new LambdaListenerTest();
}
private JButton button;
public ClickMeLambdaTest() {
setTitle("Lambda Expression Test");
button = new JButton("Click Me!");
button.addActionListener(ae -> button1Click()); // lambda expression for ActionListener
getContentPane().add(button, BorderLayout.NORTH);
setSize(450, 300);
setLocationRelativeTo(null);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
private int clickCount = 0;
public void button1Click() {
clickCount++;
if(clickCount == 1)
button.setText("Clicked!!!");
else
button.setText("Clicked " + clickCount + " times!!!");
}
}Output
Updated on: 10-Jul-2020
935 Views
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