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


public class EntenduTer extends JPanel { 
    public EntenduTer() {
	setPreferredSize(new Dimension(200, 200));
	addMouseListener(new MouseAdapter() {
		public void mouseEntered(MouseEvent e) {
		    setBackground(Color.GREEN);
		}
		
		public void mouseExited(MouseEvent e)  {
		    setBackground(Color.RED);
		}
	    }
	    );
	setBackground(Color.RED);
    }
}    

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

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