help me guys

hi please give me a solution for the below problem

I need d following output :

in AAA thread
in BBB thread
in AAA thread
in BBB thread
in AAA thread
in BBB thread

help me

Welcome to JavaRanch.

If you need a certain sequence of events you shouldn't use concurrency - it's up to the JVM how independent threads are scheduled. A combination of wait() and notify() calls can probably achieve what you're asking, but again - if the order of execution is fixed, what's the point of using two threads?

In the future, please UseCodeTags. It's unnecessarily hard to read the code otherwise, making it less likely that people will bother to do so. I have added them for you here. Also please UseAMeaningfulSubjectLine and KeepItDown.

Hi ,
Ya fine. can you send me the proper code for that problem, i already tried with wait & notify, but still i'm struggling with that.

JavaRanch is NotACodeMill. What do you have so far, and where are you stuck making progress?

In the following code, iam getting null pointer exception

import java.io.*;
import java.util.*;
import java.lang.*;

class first implements Runnable
 { boolean signalf=true;
 second obj=new second();
int i=0;
	@Override
	public synchronized  void  run() {
		while(signalf){
		
			for(;i<6;i++){
				System.out.println("a");
				signalf=false;
				obj.signals=true;
				try {
					wait();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
				
			}
	
		}
	
	}
	public void stop()
	{
		signalf=false;
	}
	
}

class  second implements Runnable
 {
	 first objs;
 boolean signals=true;
 int i=0;
	@Override
	public synchronized  void run() {
		// TODO Auto-generated method stub
		while(signals){
			for(;i<6;i++){
				System.out.println("b");
				signals=false;
				objs.signalf=true;
				notifyAll();
				
			}
	
		}
		
	}
	public void stop()
	{
		signals=false;
	}
	
	
}
 public class subbuthread  {
	 public static void main(String[] args){
		 
		 first f= new first();
		 Thread ft =new Thread(f);
		 second s =new second();
		 Thread st =new Thread(s);
		 st.start();
		 System.out.println("***********************");
		 ft.start();
		 try {
			Thread.sleep(30*1000);
		} catch (InterruptedException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		 ft.stop();
		 st.stop();
		 
		 
		 
	 }
 }

[henry: added code tags]

sun son wrote:In the following code, iam getting null pointer exception

The npe is cause by the fact that your second object is trying to access (line 48) a first reference (line 38) that it never initialized.

Henry

Please UseAMeaningfulSubjectLine and KeepItDown. I have removed the all uppercase for you.

Hi All, I have done it in following way:

public class ThreadTest {
	public static void main(String[] args) {

Director director = new Director();
		Thread runA = new A(director);
		Thread runB = new B(director);

director.setLastThread(runB);

runA.start();
		runB.start();

try {
			Thread.sleep(30000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}

class Director {
	Runnable lastThread;

synchronized public void setLastThread(Runnable lastThread) {
		this.lastThread = lastThread;
	}

synchronized boolean isAllowed(Runnable lastThread) {
		if (lastThread != this.lastThread) {
			return true;
		}
		return false;
	}
}

class A extends Thread {
	Director director;

public A(Director director) {
		this.director = director;
	}

public void run() {
		for (int i = 0; i < 3; i++) {
			synchronized (director) {
				if (!director.isAllowed(this)) {
					try {
						director.wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}

System.out.println("in AAA thread");
				director.setLastThread(this);
				director.notifyAll();
			}
		}
	}
}

class B extends Thread {
	Director director;

public B(Director director) {
		this.director = director;
	}

public void run() {
		for (int i = 0; i < 3; i++) {
			synchronized (director) {
				if (!director.isAllowed(this)) {
					try {
						director.wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}

System.out.println("in BBB thread");
				director.setLastThread(this);
				director.notifyAll();
			}
		}
	}
}

have a nice day
Michal

Hi Michel,

Thanks a lot dude:-)

Hi Michel,

I am having a doubt, by making use of 2 thread alone, can i able 2 synchronize them ?

"sun son", please check your private messages for an important administrative matter. Again.

Hi, Thomas. Could you say something more about your doubts? Both threads use synchronized block on the same common object "director", so only one thread can be inside this block at a time. Besides the methods in "Director" class needn't be synchronized, becouse you call them from synchronized block.
Bye