Java JButton handle mouse event

import java.awt.Component;
import java.awt.GridLayout;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JButton;
import javax.swing.JFrame;

class MouseEnterFocusMover extends MouseAdapter {
   public void mouseEntered(MouseEvent mouseEvent) {
      Component component = mouseEvent.getComponent();
      if (!component.hasFocus()) {
         component.requestFocusInWindow();
      }/*  w  w  w.  j  ava 2  s . c  om*/
   }
}

public class Main {
   public static void main(String args[]) {
      JFrame frame = new JFrame("Focus Sample");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      MouseListener mouseListener = new MouseEnterFocusMover();
      frame.setLayout(new GridLayout(3, 3));
      JButton button = new JButton("0");
      button.addMouseListener(mouseListener);
      button.setFocusable(false);
      frame.add(button);

      button = new JButton("1");
      button.addMouseListener(mouseListener);
      frame.add(button);

      button = new JButton("2");
      button.addMouseListener(mouseListener);
      frame.add(button);
      
      frame.setSize(300, 200);
      frame.setVisible(true);
   }
}

import java.awt.FlowLayout;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;

import javax.swing.JButton;
import javax.swing.JFrame;

public class Main extends JFrame {
  JButton mouseButton = new JButton("Mouse");

  public Main() {
    super("Handling Mouse Event");
    this.setDefaultCloseOperation(EXIT_ON_CLOSE);
    this.setLayout(new FlowLayout());
    this.getContentPane().add(mouseButton);

    // Add a MouseListener to the JButton
    mouseButton.addMouseListener(new MouseListener() {
      @Override/*from  w  w  w  .  j  a v  a 2  s  .  com*/
      public void mouseClicked(MouseEvent e) {
      }

      @Override
      public void mousePressed(MouseEvent e) {
      }

      @Override
      public void mouseReleased(MouseEvent e) {
      }

      @Override
      public void mouseEntered(MouseEvent e) {
        mouseButton.setText("Mouse has entered!");
      }

      @Override
      public void mouseExited(MouseEvent e) {
        mouseButton.setText("Mouse has exited!");
      }
    });
  }

  public static void main(String[] args) {
    Main frame = new Main();
    frame.pack();
    frame.setVisible(true);
  }
}