Update doesn't work as expected?

[RexBox]

Hello, I am following a Java-Youtube tutorial, and while I I did some tesing, my code didn't work as expected.

It is ment to print "Works" 3 times, every 17 ticks.

Here is my code:

import java.applet.Applet;

public class MainRunner extends Applet implements Runnable

{
	Ball b, b2, b3;
	
	
	public void start() //in the begin
	
	{
		Thread GameRunner = new Thread(this); //making the thread
		GameRunner.start(); //starting the thread
		b = new Ball();
		b2 = new Ball();
		b3 = new Ball();
	}

	
	public void run() //all the way along
	
	{
		while (true) //making sure the game keeps running
			
			{	
			
			b.update(this);
			b2.update(this);
			b3.update(this);
		
			try
		
			{
				Thread.sleep(17); //making the game wait for some time, to make sure it doesn't freeze
			}
		
			catch (InterruptedException e)
		
			{
				System.out.println("Failed!, because of" + e); //if it fails to wait for the exact amount of time, it prints the reason
			}
		}
	}
}

And

public class Ball 

{
	public Ball()
	
	{}
	public void update(MainRunner MR) //Every update
	
	{
		System.out.println("works");
	}
}

Now, it gives me the error;

Exception in thread "Thread-3" java.lang.NullPointerException
at MainRunner.run(MainRunner.java:27)
at java.lang.Thread.run(Unknown Source)

And it doesn't print anything at all? Any help would be really appriciated :)

NOTE: This is not my actualy program, I removed the unnecesary parts that didn't have to do anything with the error.

[DarrylBurke]

Are you sure you want to start() the Thread before the Ball variables are initialized?

db

[RexBox]

Are you sure you want to start() the Thread before the Ball variables are initialized?

db

Well, I tried it, and it works now! No idea why the other wouldn't work, but thanks alot :D.

[DarrylBurke]

No idea why the other wouldn't work

Step through the lines of code in your mind. Or is it that you don't really know what Thread#start() does?

That's not a rhetorical question, by the way. If you don't understand the chronology -- the sequence -- of code execution, you're going to face bigger problems ahead.

db