import javax.swing.JPanel;
import javax.swing.JFrame;
import java.awt.event.MouseListener;
import java.awt.event.MouseEvent;
import java.awt.Dimension;
import java.awt.Color;

public class Entendu extends JPanel implements MouseListener { 
    public Entendu() {
	setPreferredSize(new Dimension(200, 200));
	addMouseListener(this);
	setBackground(Color.RED);
    }

    public void mouseEntered(MouseEvent e) {
	setBackground(Color.GREEN);
    }
    
    public void mouseExited(MouseEvent e)  {
	setBackground(Color.RED);
    }
    
    public void mousePressed(MouseEvent e)  {}
    
    public void mouseReleased(MouseEvent e) {}
    
    public void mouseClicked(MouseEvent e) {}
}   

class EssaiEntendu {
    public static void main(String[] arg) {
	JFrame fenetre = new JFrame();
	fenetre.setContentPane(new Entendu());

	fenetre.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	fenetre.pack();
	fenetre.setLocation(300, 300);
	fenetre.setVisible(true);
    } 
}