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inner class

kofi ofei
Ranch Hand

Joined: May 22, 2005
Posts: 39
the following programme below compiles but when i run it nothing is displayed in the applet viewer

import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class InnerClasses extends Applet{
String m;
public InnerClasses(){
MyListener m = new MyListener();
//start an inner class called MyListener
public final class MyListener extends MouseAdapter{
public void mouseClicked(MouseEvent e){
if(e.getClickCount()== 1) m = "Single click";
else if(e.getClickCount()== 2) m = "Double click";
int mod = e.getModifiers();
if((mod & InputEvent.BUTTON1_MASK) !=0) m += "Button1";
else if((mod & InputEvent.BUTTON1_MASK)!=0) m += "Button2";
if(e.isAltDown()) m += "ALT key is down";
if(e.isControlDown()) m += "CONTROL key is down";
if(e.isShiftDown()) m += "SHIFT key is down";
public void paint(Graphics g){
g.setFont(new Font("Serif",Font.PLAIN,18));
g.drawString(m, 10, 80);
Mark Spritzler

Joined: Feb 05, 2001
Posts: 17260

Moving to Java In General (Beginner) forum.


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Marilyn de Queiroz

Joined: Jul 22, 2000
Posts: 9056
I think when the applet starts, it tries to "paint" itself, but at that point in time, 'm' is still null. So the applet throws a NullPointerException and dies.

"Yesterday is history, tomorrow is a mystery, and today is a gift; that's why they call it the present." Eleanor Roosevelt
Marilyn de Queiroz

Joined: Jul 22, 2000
Posts: 9056
Also, formatting your code will help people who want to try to help you.

[ May 22, 2005: Message edited by: Marilyn de Queiroz ]
Consider Paul's rocket mass heater.
subject: inner class