Using Timeout to avoid deadlock in Java multithreading

Here is a contrived example with 2 locks and 2 threads that try to acquire them in different orders. Without the timeout, the code would deadlock.

public static void main(String[] args) throws Exception {    final ReentrantLock lock1 = new ReentrantLock();    final ReentrantLock lock2 = new ReentrantLock();    Runnable try1_2 = getRunnable(lock1, "lock 1", lock2, "lock 2");    Runnable try2_1 = getRunnable(lock2, "lock 2", lock1, "lock 1");    new Thread(try1_2).start();    new Thread(try2_1).start();}private static Runnable getRunnable(final ReentrantLock lock1, final String lock1Name, final ReentrantLock lock2, final String lock2Name) {    return new Runnable() {        @Override        public void run() {            try {                if (lock1.tryLock(1, TimeUnit.SECONDS)) {                    System.out.println(lock1Name + " acquired in thread " + Thread.currentThread());                    if (lock2.tryLock(1, TimeUnit.SECONDS)) {                        System.out.println(lock2Name + " acquired in thread " + Thread.currentThread());                        Thread.sleep(2000);                    } else {                        System.out.println("Could not acquire "+lock2Name + " in thread " + Thread.currentThread());                        lock1.unlock();                        System.out.println(lock1Name + " released in thread " + Thread.currentThread());                    }                } else {                    System.out.println("Could not acquire " + lock1Name + " in thread " + Thread.currentThread());                }            } catch (InterruptedException e) {                //you should not ignore it            } finally {                if (lock1.isHeldByCurrentThread()) lock1.unlock();                if (lock2.isHeldByCurrentThread()) lock2.unlock();            }        }    };}

may this help,

Lock lock = null;lock=....;if (lock.tryLock(15L, TimeUnit.SECONDS)) {    try {       ........    } finally {        lock.unlock();    }} else {      // do sumthing}

Lock in Java

Use tryLock(timeout, timeunits);

Acquires the lock if it is free within the given waiting time and the current thread has not been interrupted. If the lock is available this method returns immediately with the value true.

If the lock is not available then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

The lock is acquired by the current thread;

or Some other thread interrupts the current thread, and interruption of lock acquisition is supported;

or The specified waiting time elapses