Please suggest ways to cause deadlock in this code

[Rahul Sudip Bose]

Here is working code. Please suggest ways to ensure deadlock or increase the probability of deadlocking :

public class Hug implements Runnable 
{
	static Thread t1;
	static Hold h, h2;
	public void run() 
	{
		if(Thread.currentThread().getId() == t1.getId()) h.adjust();
		else h2.view(); 
	}
	
	public static void main(String[] args) 
	{
		h = new Hold();
		h2 = new Hold();
		t1 = new Thread(new Hug());
		t1.start();
		new Thread(new Hug()).start();
		
	}
	
}
 
class Hold 
{
	static int x = 5;
	synchronized void adjust() 
	{
		System.out.print(x-- + " ");
		try { Thread.sleep(200); } catch (Exception e) { ; }
		view();
	}
	
	synchronized void view() 
	{
		try { Thread.sleep(200); } catch (Exception e) { ; }
		if(x > 0) adjust();
	} 
	
}

[Matthew Brown]

You want a deadlock?

Easiest way to get a deadlock is to have the two threads require a lock on two separate objects, but for them to acquire them in different orders. For example:

final Object a = new Object();
final Object b = new Object();

Thread t1 = new Thread(new Runnable() {
    public void run() {
        synchronized(a) {
            try { Thread.sleep(200); } catch (InterruptedException e) { }  
            synchronized(b) {
                // do something 
            }
        }
    }
});

Thread t2 = new Thread(new Runnable() {
    public void run() {
        synchronized(b) {
            try { Thread.sleep(200); } catch (InterruptedException e) { }  
            synchronized(a) {
                // do something 
            }
        }
    }
});

t1.start();
t2.start();

In your example, it appears that the first thread is always synchronizing on h, and the second on h2. They share the same static int, so you may well get confusing behaviour, but I don't see how a deadlock can occur. You need both threads to be waiting for each other.