Mouse Actions in Java Swing Example

import javax.swing.*; 
 import java.awt.*; 
 import java.awt.event.*; 
 public class JMouseActionsJavaExample extends JFrame implements MouseListener 
    { 
          private final int MAXX = 30; 
          private final int STRTX = 20; 
          private final int STRTY = 30; 
          private int x, y; 
          private String message[] = new String[MAXX]; 
          private int msgCount = 0; 
          public JMouseActionsJavaExample() 
            { 
                 setTitle("Mouse Actions in Java With Swing"); 
                 setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); 
                 addMouseListener(this); 
            } 
                   public void mouseClicked(MouseEvent e) 
                       { 
                            int WchBtn = e.getButton(); 
                            String msg; 
                            if(msgCount == MAXX) 
                            clearScreen(); 
                            message[msgCount] = "You pressed the mouse."; 
                            if(WchBtn == MouseEvent.BUTTON1) 
                            msg = "Button One."; 
                            else if(WchBtn == MouseEvent.BUTTON1) 
                            msg = "Button Two."; 
                            else msg = "Button Three."; 
                            message[msgCount] = message[msgCount] +" You used " + msg; 
                            message[msgCount] = message[msgCount] +" You are at position " +e.getX() + ", " + e.getY() + "."; 
                            if(e.getClickCount() == 2) 
                            message[msgCount] = message[msgCount] +" You Clicked Double"; 
                              else 
                             message[msgCount] = message[msgCount] +" You Clicked Single";++msgCount; 
                             repaint(); 
                       } 
                             public void mouseEntered(MouseEvent e) 
                               { 
                                    if(msgCount == MAXX) 
                                    clearScreen(); 
                                    message[msgCount] = "You Enterd in Frame"; 
                                   ++msgCount; 
                                    repaint(); 
                              } 
                                    public void mouseExited(MouseEvent e) 
                                        { 
                                            if(msgCount == MAXX) 
                                            clearScreen(); 
                                            message[msgCount] = "Now You Exit From Frame"; 
                                            ++msgCount; 
                                            repaint(); 
                                        } 
                                            public void mousePressed(MouseEvent e){} 
                                            public void mouseReleased(MouseEvent e){} 
                                            public void paint(Graphics gr) 
                                               { 
                                                  final int SIZE = 25; 
                                                  super.paint(gr); 
                                                  x = STRTX; 
                                                  y = STRTY; 
                                                  for(int a = 0; a < msgCount; ++a) 
                                                  gr.drawString(message[a], x, y += SIZE); 
                                               } 
                                                  public void clearScreen() 
                                                    { 
                                                        msgCount = 0; 
                                                        for(int a = 0; a < MAXX; ++a) 
                                                        message[a] = " "; 
                                                        repaint(); 
                                                    } 
                                                        public static void main(String[] as) 
                                                             { 
                                                                  JMouseActionsJavaExample frm = new JMouseActionsJavaExample(); 
                                                                  final int WIDTH = 750; 
                                                                  final int HEIGHT = 300; 
                                                                  frm.setSize(500,500); 
                                                                  frm.setVisible(true); 
                                                              } 
     }