Thread: Getting "AWT-EventQueue-0" java.lang.NullPointerException error

Here is the error I am getting:

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at Main_Box_Game.mouseEntered(Main_Box_Game.java:149)
at java.awt.AWTEventMulticaster.mouseEntered(AWTEvent Multicaster.java:283)
at java.awt.Component.processMouseEvent(Component.jav a:6310)
at java.awt.Component.processEvent(Component.java:606 6)
at java.awt.Container.processEvent(Container.java:208 5)
at java.awt.Component.dispatchEventImpl(Component.jav a:4667)
at java.awt.Container.dispatchEventImpl(Container.jav a:2143)
at java.awt.Component.dispatchEvent(Component.java:44 97)
at java.awt.LightweightDispatcher.retargetMouseEvent( Container.java:4600)
at java.awt.LightweightDispatcher.trackMouseEnterExit (Container.java:4389)
at java.awt.LightweightDispatcher.processMouseEvent(C ontainer.java:4246)
at java.awt.LightweightDispatcher.dispatchEvent(Conta iner.java:4194)
at java.awt.Container.dispatchEventImpl(Container.jav a:2129)
at java.awt.Window.dispatchEventImpl(Window.java:2475 )
at java.awt.Component.dispatchEvent(Component.java:44 97)
at java.awt.EventQueue.dispatchEvent(EventQueue.java: 635)
at java.awt.EventDispatchThread.pumpOneEventForFilter s(EventDispatchThread.java:296)
at java.awt.EventDispatchThread.pumpEventsForFilter(E ventDispatchThread.java:211)
at java.awt.EventDispatchThread.pumpEventsForHierarch y(EventDispatchThread.java:201)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:196)
at java.awt.EventDispatchThread.pumpEvents(EventDispa tchThread.java:188)
at java.awt.EventDispatchThread.run(EventDispatchThre ad.java:122)

Here is my code:

import acm.graphics.*;
import acm.program.*;
import java.awt.event.*;
import java.awt.Color;
import java.awt.*;
import student.*;
import java.util.*;
import acm.util.RandomGenerator;
 
// -------------------------------------------------------------------------
/**
 *  This is a game where you will attempt to click inside boxes of varying size 
 *  and will be given different point totals depending on the size of box you hit. the smaller the
 *  box the more points. If you do not hit a box you wil receive and error message
 * 
 *  @author  
 *  @version (2009.09.18)
 */
public class Main_Box_Game extends GraphicsProgram
{
    //~ Instance/static variables .............................................
        private RandomGenerator rgen = RandomGenerator.getInstance();
        private GLabel label;
        private GLabel label1;
        private GLabel label2;
        private GLabel label3;
        private GRect rect;
        private GRect rect_M;
        private GRect rect_B;
        private int SCORE, points, clicks, misses, games;
        private boolean largeBoxHit, medBoxHit, smallBoxHit;
 
 
 
 
 
 
 
 
 
 
 
    //~ Constructor ...........................................................
 
    // ----------------------------------------------------------
    /**
     * Creates a new Invisible_Box_Game object.
     */
 
 
 
 
    //~ Methods ...............................................................
 
    public void init() {
 
        addMouseListeners();
        label = new GLabel("Click mouse to hit box and be awarded points or lose 1 point for every miss. If you hit all 3 boxes", 10, 50 );
        label1 = new GLabel("receive 200, but beware they are different sizes. Small, med, little. If you hit the med and small get", 10, 150);
        label2 = new GLabel("150 points, 125 for large and small, 100 for just the small 75 for med, and 50 for large only.you do not", 10, 250);
        label3 = new GLabel("get more points added hitting the boxes more than once, and you can play as many times you want. have fun", 10, 350);
        add (label);
        add (label1);
        add (label2);
        add (label3);
        pause(3500);
        label.setLabel ("");
        label1.setLabel ("");
        label2.setLabel ("");
        label3.setLabel ("");
        rect1();
        add (rect) ;
        rect2();
        add (rect_M);
        rect3();
        add (rect_B);
       largeBoxHit = false;
       medBoxHit = false;
       smallBoxHit= false;
        SCORE= 0;
       clicks= 0;
       misses= -1;
       games= 0;
    } 
 
 
 
 
 
   public void rect1()
        {
           Random gen = new Random() ;
           int smallx = gen.nextInt(470) ;
           int smally= gen.nextInt(470);
           rect = new GRect (30, 30, 30, 30);
           rect.setLocation (smallx, smally); 
           rect.setFilled(true);
           rect.setFillColor (Color.GREEN);
        } 
 
 
 
    public void rect2()
        {
 
           Random gen1 = new Random() ;
           int mediumx = gen1.nextInt(455) ;
           int mediumy= gen1.nextInt(455);
           rect_M = new GRect (45, 45, 45,45) ;
           rect_M.setLocation (mediumx, mediumy);
           rect_M.setFilled(true);
           rect_M.setFillColor (Color.BLUE);
        }  
 
 
 
 
    public void rect3()
        {   
          Random gen2 = new Random() ;
           int bigx = gen2.nextInt(420) ;
           int bigy= gen2.nextInt(420);
          rect_B = new GRect (80, 80, 80,80) ;
           rect_B.setLocation (bigx, bigy);
           rect_B.setFilled(true);
           rect_B.setFillColor (Color.RED);
 
        }
 
 
 
    public void mouseExited(MouseEvent e)
      {
        rect.setVisible (true);
        rect_M.setVisible(true);
        rect_B.setVisible(true);
        games= games + 1;
        println ("games played" + games + ".");  
        println ("Your score is " + SCORE + ".");
        println ("Your clicks are " + clicks + ".");
 
 
      }  
 
 
    public void mouseEntered(MouseEvent e)
          {
 
Line149**         [COLOR="Red"]   rect.setVisible(false);[/COLOR]
            rect_M.setVisible(false);
            rect_B.setVisible(false);
            SCORE=0;
            clicks=0;
            largeBoxHit = false;
            medBoxHit = false;
            smallBoxHit= false;
            misses=0;
 
         }
 
 
   public void mouseDragged(MouseEvent e)
    {
        rect.setVisible(true);
        rect_M.setVisible(true);
        rect_B.setVisible(true);
    }
 
 
    public void mouseClicked(MouseEvent e)
    {
 
 
      clicks++;
      misses--;
 
     if(rect.contains(e.getX(), e.getY()))
 
      {
           smallBoxHit = true;
       }
 
      if(rect_M.contains(e.getX(), e.getY())) 
 
       {
           medBoxHit = true;
       }
 
      if(rect_B.contains(e.getX(), e.getY())) 
 
      {
           largeBoxHit = true;
      }
        if(largeBoxHit && medBoxHit && smallBoxHit)
       SCORE= 200 + misses;
        else if(medBoxHit && smallBoxHit)
       SCORE= 150+ misses;
 
       else if(largeBoxHit && smallBoxHit)
       SCORE= 125+ misses;
 
       else if(largeBoxHit && medBoxHit)
       SCORE = 110+ misses;
 
       else if (smallBoxHit)
       SCORE=  100 + misses;
       else if (medBoxHit)
       SCORE= 75+ misses;
       else if(largeBoxHit)
       SCORE= 50+ misses;
       else{
       SCORE= misses + 1;
       }
 
    }   
 
}