How to acquire multiple locks without ordering constraints in Java?

Question

So I have code similar to this

synchronized(objectOne){ do stuff }
synchronized(objectTwo){ do stuff }

The problem with this is the program will wait for the lock on objectOne, even if the lock for objectTwo is available. What I'm trying to do is say: try to lock both objectOne and objectTwo, and whichever lock you get first do the stuff for that lock. I've come up with a solution but I think it's rather hacky and I'm wondering if anybody has any better ideas.

Here's my idea: Start 2 threads, each one waiting on a lock and then the main thread will wait on a CountDownLatch. So you end up with something like this:

CountDownLatch latch = new CountDownLatch(2);

new Thread(new Runnable(){
public void run(){
    synchronized(objectOne) { do stuff }
    latch.countDown();
}).start();

new Thread(new Runnable(){
public void run(){
    synchronized(objectTwo) { do stuff }
    latch.countDown();
}).start();

latch.await();

Answer 1

I think you should use Lock which provides you with the method boolean tryLock().

Returns: true if the lock was acquired and false otherwise

Proceed with do stuff when you have at least one of the locks.

Answer 2

You might want to have 2 queues of jobs, 2 threads each polling a queue and execute the jobs.

For jobs related to objectOne, you put it in queue#1; jobs related to objectTwo in queue#2.

worker1.queue.put( new Runnable(){ public void run() { do stuff } } );
worker2.queue.put( new Runnable(){ public void run() { do stuff } } );

----

class Worker extends Thread

    BlockingQueue<Runnable> queue = new LinkedBlockingQueue<>();

    public void run()
        while(true)
            queue.take().run();