Solved

Problem with Apllet (Deprecation)

Posted on 1997-07-06
3
258 Views
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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
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 .

0

Featured Post

Free Tool: Subnet Calculator

The subnet calculator helps you design networks by taking an IP address and network mask and returning information such as network, broadcast address, and host range.

One of a set of tools we're offering as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction Java can be integrated with native programs using an interface called JNI(Java Native Interface). Native programs are programs which can directly run on the processor. JNI is simply a naming and calling convention so that the JVM (Java…
Basic understanding on "OO- Object Orientation" is needed for designing a logical solution to solve a problem. Basic OOAD is a prerequisite for a coder to ensure that they follow the basic design of OO. This would help developers to understand the b…
Viewers learn about the third conditional statement “else if” and use it in an example program. Then additional information about conditional statements is provided, covering the topic thoroughly. Viewers learn about the third conditional statement …
Viewers will learn about the different types of variables in Java and how to declare them. Decide the type of variable desired: Put the keyword corresponding to the type of variable in front of the variable name: Use the equal sign to assign a v…

717 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question