"To use the ActionListener interface it must be implemented by a class and must override" code example

Example 1: actionListener java

import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

/*in main*/
button.addActionListener(new ActionListener() {
  public void actionPerformed(ActionEvent e) {
			System.out.println('x');
  }
});

Example 2: java swing button on click

JButton b = new JButton("push me");
b.addActionListener(new ActionListener() {

    @Override
    public void actionPerformed(ActionEvent e) {
        //your actions
    }
});