//This is the error:

Exception in thread "main" java.lang.NullPointerException
	at begin.main(begin.java:82)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:597)
	at com.intellij.rt.execution.application.AppMain.main(AppMain.java:90)





//code below

import javax.swing.*;
import java.awt.*;
import java.util.Random;

/**
 * Created by IntelliJ IDEA.
 * User: User
 * Date: 29/06/2007
 * Time: 13:25:52
 * To change this template use File | Settings | File Templates.
 */
public class begin {

    public void particle(int x, int y){

    }
   public static void main(String[] args){
       JFrame frame = new JFrame("Fire Furry");
       Graphics g = frame.getGraphics();
       int particleAmount = 500;
       int startx = 20;
       int starty = 20;
       Color[] particleColor = new Color[particleAmount];
       Color[] particleColorList = {Color.RED, Color.ORANGE, Color.WHITE};
       int[] particleX = new int[particleAmount];
       int[] particleY = new int[particleAmount];
       int[] particleVeloX = new int[particleAmount];
       int[] particleVeloY = new int[particleAmount];

       //Create Random Generator Spock Styles.
       random random = new random();
       Thread randomThread = new Thread(random);
       randomThread.start();

       // Set random amount.
       random.maxRandom = 3;
       random.delay = 10; //ms before new number is generated.

       

       //Set Particle Starting point.
       for(int i = 0;i<particleAmount;i++){
         particleX[i] = startx;
         particleY[i] = starty;
       }

       //Set Random Velocity.
       for(int i = 0;i<particleAmount;i++){
           particleVeloX[i] = random.random - (random.maxRandom / 2);
           particleVeloY[i] = random.random - (random.maxRandom / 2);
       }

       //Set Random Colors.
       random.maxRandom = 2;

       for(int i = 0;i<particleAmount;i++){
         particleColor[i] = particleColorList[random.random];
         System.out.println(particleColor[i]);
       }

       //Set Frame Requirements (Size, Location).
       frame.setSize(200,200);
       frame.setLocation(30,30);
       frame.show();

       //Begin main loop.
       random.maxRandom = 2;
       while(true){

       
           //Move Particles

           for(int i = 0;i<particleAmount;i++){
               particleX[i] = particleX[i] + particleVeloX[i];
               particleY[i] = particleY[i] + particleVeloY[i];

               // If particle off screen. Set new values.
               if(particleX[i] > frame.getWidth() || particleY[i] > frame.getHeight() || particleX[i] < 0 || particleY[i] < 0){
                   particleX[i] = startx; particleY[i] = starty;
                   particleColor[i] = particleColorList[random.random];
               }
           }

           //Draw particles.
           for(int i = 0;i<particleAmount;i++){
            g.setColor(Color.RED);//particleColor[i]);
            g.drawLine(particleX[i],particleY[i],particleX[i],particleY[i]);
            frame.paintAll(g);
           }
       }




   }
}