Null Pointer Exception

[Dustman]

Okay.. I'm pretty new to java and I'm trying to write a simple program that draws several circles on the screen when loaded. I made a class called WormCircle that holds all the cordinates and a few other values for each one. The parent class is Shape. Everything compiles right but when I run it, I get a null pointer exception from my paint method.

//WormAttack.java
import java.io.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;

public class WormAttack extends JApplet {

    //Allows applet to be ran as an application.
    public static void main(String[] args) {
    JFrame f = new JFrame("Worm Attack");
    WormAttack game = new WormAttack();
    game.init();
    f.getContentPane().add(game,"Center");
    f.setSize(640,480);
    f.setVisible(true);
    f.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {
                System.exit(0);
        }
    });

    }
      
    /****Variables****/
    public int level;
    public WormCircle[] worm;
        
    /****Methods*****/
    public void init()
    {
        setupGame(5);
    }
        
    public void setupGame(int lev)
    {
        level = lev;
        int tmp;
        int newX = 640;
        worm = new WormCircle[level];
           
        for(tmp = 0; tmp >= level - 1; tmp++)
        {
            worm[tmp] = new WormCircle(newX,0);
            newX -= 15;
        }
    }
        
    public void paint(Graphics g)
    {
        for(int x = 0;x<worm.length;x++)
	{
            worm[x].draw(g);
        }
    }
}//End of WormAttack.java

I'm pretty sure everything is set up right. I just keep getting the null pointer exception when I try to run. Does the paint method automaticly run when I add a new item to my array? If so.. how do I keep it from painting untill the array is full? -Dustin
Rom 8:28

 

[Reddy316]

Hi,
If u see the working of the for loop, it works like this, the for loop executes while the condition u specify is true. but if u see in
"for(tmp = 0; tmp >= level - 1; tmp++)"

it will execute only once i.e for tmp = 0 because the next time it comes to the condition check, a false will be returned thats why only worm[0] is present and all other values for worm will be null.. i think u should change ur for loop to for(tmp = 0; tmp <= level - 1; tmp++) and check the working of ur program..

Hope this helps,
Reddy316

 

[Dustman]

Arr.. I can't believe I missed that. I must have just hit the wrong key when I originally typed it. Its so frustrating to spend hours trying to fix something like that... I was about to go crazy. Thank you so much for pointing it out.. it works great now. -Dustin
Rom 8:28