Synchronization vs Lock

java multithreading concurrency synchronization java.util.concurrent
daydreamer picture daydreamer · Nov 17, 2010 · Viewed 159.9k times · Source

java.util.concurrent API provides a class called as Lock, which would basically serialize the control in order to access the critical resource. It gives method such as park() and unpark().

We can do similar things if we can use synchronized keyword and using wait() and notify() notifyAll() methods.

I am wondering which one of these is better in practice and why?

Answer

Steven Schlansker picture Steven Schlansker · Nov 17, 2010

If you're simply locking an object, I'd prefer to use synchronized

Example:

Lock.acquire();
doSomethingNifty(); // Throws a NPE!
Lock.release(); // Oh noes, we never release the lock!

You have to explicitly do try{} finally{} everywhere.

Whereas with synchronized, it's super clear and impossible to get wrong:

synchronized(myObject) {
    doSomethingNifty();
}

That said, Locks may be more useful for more complicated things where you can't acquire and release in such a clean manner. I would honestly prefer to avoid using bare Locks in the first place, and just go with a more sophisticated concurrency control such as a CyclicBarrier or a LinkedBlockingQueue, if they meet your needs.

I've never had a reason to use wait() or notify() but there may be some good ones.

Related questions

How do synchronized static methods work in Java and can I use it for loading Hibernate entities?

If I have a util class with static methods that will call Hibernate functions to accomplish basic data access. I am wondering if making the method synchronized is the right approach to ensure thread-safety. I want this to prevent access …

Read More
Are LinkedBlockingQueue's insert and remove methods thread safe?

I'm using LinkedBlockingQueue between two different threads. One thread adds data via add, while the other thread receives data via take. My question is, do I need to synchronize access to add and take. Is LinkedBlockingQueue's insert and remove methods …

Read More
Performance of synchronize section in Java

I had a small dispute over performance of synchronized block in Java. This is a theoretical question, which does not affect real life application. Consider single-thread application, which uses locks and synchronize sections. Does this code work slower than the …

Read More