How to call two threads alternatively

[Abhra Kar]

Hi ,

I have two threads, say Thread-1(print 1) and Thread-2(print 2). How I can call them in loop such that they will execute alternatively,
Output---  1 2 1 2 1 2 .....

Below code give me a output ----- 1 2 2 2 2 2 1 and then release the lock but no thread available to get the lock .

public class ThreadTest {

	public static void main(String[] args) throws InterruptedException {
		Count count = new Count();
		Thread t1 = new Thread(new Thread1(count));
		t1.setPriority(5);
		Thread t2 = new Thread(new Thread2(count));
		t2.setPriority(10);
		t1.start();
		t2.start();
	}
}

class Thread1 implements Runnable {
	Count count = null;
	Thread1(Count count) {
		this.count = count;
	}

	public void run() {
		synchronized (count) {
			for (int i = 0; i < 5; i++) {
				count.print1();
				try {
					count.wait();
				} catch (InterruptedException e) {
				}
			}
		}
	}
}

class Thread2 implements Runnable {
	Count count = null;

	Thread2(Count count) {
		this.count = count;
	}

	public void run() {
		for(int i=0;i<5;i++){
			synchronized (count) {
				count.print2();
				count.notify();
			}	
		}
		
	}
}

class Count {
	void print1() {
		System.out.println("1");
	}

	void print2() {
		System.out.println("2");
	}
}

How we I can modify the code ?
Thanks

[Junilu Lacar]

Why would you want to do that? If you need operations to be executed in a specific order, using threads is not how to do it. That's diametrically opposite of what threads are meant for, which is independent processing.

Use the right tool instead of trying to find a way to use the wrong tool to fit your purpose.

[Abhra Kar]

That's true. But is there any option so that we can achieve this.

[Junilu Lacar]

Abhra Kar wrote:That's true. But is there any option so that we can achieve this.

If you're going to do it with two threads, the first thing that comes to mind is a semaphore that the two threads can check/set. Seems like it would be kind of kludgy though. What methods of thread have you studied so far -- that might give us a clue as to what your instructor is looking for.

See semaphores and mutexes

Again, I don't see this as a typical use case for threads. In fact, I think it's antithetical.

[Abhra Kar]

Hi Junilu,
               Thanks for the idea. My knowledge limited to wait, notify , coundownlatch , cyclicbarrier .Semhaphoe and mutex still I haven't studied.I will check those and get back for any query.

Thanks
Abhra