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Problem with Apllet (Deprecation)

Posted on 1997-07-06
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Last Modified: 2012-05-04
I am messing around with an applet I got from Java Boutique
and am getting some warnings involved with deprecated methods. If Iignore thesewarnings and use the class anyways I get a NullPointer error.

I am using jdk113.
The method is something like Dimension Size()
 
Here is the applet:

//* <C> 1996 Growler Software, Inc. *//
import java.awt.*;
import java.applet.*;
import java.lang.*;
import java.util.*;
import java.net.*;

public class Firework extends Applet implements Runnable
{
public int AnimationSpeed,
           RocketStyleVariability,
           MaxRocketNumber,
           MaxRocketExplosionEnergy,
           MaxRocketPatchNumber,
           MaxRocketPatchLength,
           Gravity;
public String RocketSoundtrack;

private int mx=20,my=20;
private Thread thread=null;

private Rocket rocket[];

public void init()
   {
   int i;
   String p;

   p=getParameter("AnimationSpeed");   AnimationSpeed=(p==null)?100:Integer.valueOf(p).intValue();

   RocketSoundtrack=getParameter("RocketSoundtrack");
   p=getParameter("RocketStyleVariability");
   RocketStyleVariability=(p==null)?20:Integer.valueOf(p).intValue();
   p=getParameter("MaxRocketNumber");
   MaxRocketNumber=(p==null)?5:Integer.valueOf(p).intValue();
   p=getParameter("MaxRocketExplosionEnergy");
   MaxRocketExplosionEnergy=(p==null)?500:Integer.valueOf(p).intValue();
   p=getParameter("MaxRocketPatchNumber");
   MaxRocketPatchNumber=(p==null)?50:Integer.valueOf(p).intValue();
   p=getParameter("MaxRocketPatchLength");
   MaxRocketPatchLength=(p==null)?100:Integer.valueOf(p).intValue();
   p=getParameter("Gravity");
   Gravity=(p==null)?20:Integer.valueOf(p).intValue();
###############################
Here are the calls giving me theproblem
   mx=size().width-1;
   my=size().height-1;

   rocket=new Rocket[MaxRocketNumber];
   for(i=0;i<MaxRocketNumber;i++)rocket[i]=new Rocket(mx,my,Gravity);
   }
public void start()
   {
   if(thread==null)
      {
      thread=new Thread(this);
      thread.start();
      }
   }
public void stop()
   {
   if(thread!=null)
      {
      thread.stop();
      thread=null;
      }
   }
public void run()
   {
   int i,
       e=(int)(Math.random()*MaxRocketExplosionEnergy*3/4)+
         MaxRocketExplosionEnergy/4+1,
       p=(int)(Math.random()*MaxRocketPatchNumber*3/4)+
         MaxRocketPatchNumber/4+1,
       l=(int)(Math.random()*MaxRocketPatchLength*3/4)+
         MaxRocketPatchLength/4+1;
   long s=(long)(Math.random()*10000);
   boolean sleep;
   Graphics g=getGraphics();
   URL u=null;

   while(true)
      {
      try {
          thread.sleep(100/AnimationSpeed);
          }
      catch(InterruptedException x){}

      sleep=true;
      for(i=0;i<MaxRocketNumber;i++)
         sleep=sleep&&rocket[i].sleep;
      if(sleep&&Math.random()*100<RocketStyleVariability)
         {
         e=(int)(Math.random()*MaxRocketExplosionEnergy*3/4)+
           MaxRocketExplosionEnergy/4+1;
         p=(int)(Math.random()*MaxRocketPatchNumber*3/4)+
           MaxRocketPatchNumber/4+1;
         l=(int)(Math.random()*MaxRocketPatchLength*3/4)+
           MaxRocketPatchLength/4+1;
         s=(long)(Math.random()*10000);
         }

      for(i=0;i<MaxRocketNumber;i++)
         {
         if(rocket[i].sleep&&Math.random()*MaxRocketNumber*l<1)
            {
            try {
                u=new URL(getDocumentBase(),RocketSoundtrack);
                }
            catch(MalformedURLException x){}
            play(u);

            rocket[i].init(e,p,l,s);
            rocket[i].start();
            }
         rocket[i].show(g);
         }
      }
   }
public void paint(Graphics g)
   {
   g.setColor(Color.black);
   g.fillRect(0,0,mx+1,my+1);
   }
}

class Rocket
{
public boolean sleep=true;

private int energy,patch,length,
            mx,my,
            gravity,
            ox,oy,
            vx[],vy[],
            x,y,
            red,blue,green,
            t;
private Random random;

public Rocket(int a,int b,int g)
   {
   mx=a;
   my=b;

   gravity=g;
   }
public void init(int e,int p,int l,long seed)
   {
   int i;

   energy=e;
   patch=p;
   length=l;

   random=new Random(seed);

   vx=new int[patch];
   vy=new int[patch];

   red=(int)(random.nextDouble()*128)+128;
   blue=(int)(random.nextDouble()*128)+128;
   green=(int)(random.nextDouble()*128)+128;

   ox=(int)(Math.random()*mx/2)+mx/4;
   oy=(int)(Math.random()*my/2)+my/4;

   for(i=0;i<patch;i++)
      {
      vx[i]=(int)(Math.random()*energy)-energy/2;
      vy[i]=(int)(Math.random()*energy*7/8)-energy/8;
      }
   }
public void start()
   {
   t=0;
   sleep=false;
   }
public void show(Graphics g)
   {
   if(!sleep)
      if(t<length)
         {
         int i,c;
         double s;
         Color color;

         c=(int)(random.nextDouble()*64)-32+red;
         if(c>=0&&c<256)red=c;
         c=(int)(random.nextDouble()*64)-32+blue;
         if(c>=0&&c<256)blue=c;
         c=(int)(random.nextDouble()*64)-32+green;
         if(c>=0&&c<256)green=c;
         color=new Color(red,blue,green);

         for(i=0;i<patch;i++)
            {
            s=(double)t/100;
            x=(int)(vx[i]*s);
            y=(int)(vy[i]*s-gravity*s*s);

            g.setColor(color);
            g.drawLine(ox+x,oy-y,ox+x,oy-y);

            if(t>=length/2);
               {
               int j;
               for(j=0;j<2;j++)
                  {
                  s=(double)((t-length/2)*2+j)/100;
                  x=(int)(vx[i]*s);
                  y=(int)(vy[i]*s-gravity*s*s);

                  g.setColor(Color.black);
                  g.drawLine(ox+x,oy-y,ox+x,oy-y);
                  }
               }
            }

         t++;
         }
      else
         {
         sleep=true;
         }
   }
}

0
Comment
Question by:chuckd070397
3 Comments
 
LVL 2

Expert Comment

by:mgk
ID: 1222693
Hi, deprecation means that a class you're using in this code has been replaced between JDK 1.0 and JDK 1.1, compiling using "-deprecation" in the command line will tell you what classes are deprecated. The docs that come with the JDK usually tell you what a class/method is replaced by if you look the old one's up. Normally it's just a case of conforming to the get/set standards of JavaBeans, so it would be Dimension d=getSize();

I'm less sure about the null pointer, I'd probably just check you have all the parameters in your applet tag and they're all spelt the same (especially the cases)

Mark King

0
 
LVL 6

Expert Comment

by:jpk041897
ID: 1222694
Mark's answer is mostly (if not completley) correct.

I'll only add that the NULL pointer is probably caused by the fact that the deprecated methods are not understood by the VM you are running under, so the VM return NULL whenever they are called.
0
 

Accepted Solution

by:
scott99 earned 100 total points
ID: 1222695
This may likely be a timing problem.

Recall that Applet is a Panel which is a Container which is a Component.

The width and height variables are initially null and get assigned during the setBounds() (which replaces deprecated reshape() ). If setBounds was not called yet, the width and height values in the Dimension that you get back from size() have not been initialized and are null. When you subtract 1 from a null value, that is where you get a null pointer exception.

mx=size().width-1;
my=size().height-1;

You may have to postpone this calculation until the doLayout() method .

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