May Deadlock or not?

[Vladimir Scheglov]

May Deadlock or not, if yes - where?

public class DeadLockTest{
 
    public static void main(String[] args){
        A a1 = new A();
        A a2 = new A();
        Thread t1 = new Thread(new Tester(a1,a2));
        Thread t2 = new Thread(new Tester(a2,a1));
        t1.start();
        t2.start();
    }
 
    public static class Tester implements Runnable{
 
        static int nextId = 1;
 
        private A obj1;
        private A obj2;
        private int id = 0;
 
        public Tester(A obj1, A obj2){
            this.obj1 = obj1;
            this.obj2 = obj2;
            id = nextId++;
        }
 
        public void run(){
            obj1.setValue(id);
            System.out.println(obj1.equals(obj2));
        }        
    }
 
    public static class A{
 
        private int value = 0;
 
        synchronized void setValue(int value){
            this.value = value;
        }
 
        synchronized int getValue(){
            return value;
        }
 
        public synchronized boolean equals(Object o){
            A a = (A) o;
            try{
                Thread.sleep(1000);
            }catch(InterruptedException ex){
                System.err.println("Interrupted!");
            }
            return value == a.getValue();
        }
    }
}    

[Shaan Shar]

Yes Deadlock is there.

And the deadlock is occuring at System.out.println(equals ) method...


Pls correct me if I am wrong.

[Clifton Craig]

I agree.

The deadlock is in the case where thread 1 is in equals on a1 instance and waiting on the monitor for a2 instance while thread 2 is in equals on a2 instance waiting for the monitor on a1 instance.