Question

Is it possible to pass over a synchronized block of code when another thread has the synchronized object under lock? If not, is there an alternative that can act in this way?

Answer 1

You can replace the synchronized block with the java.util.concurrent.locks.ReentrantLock class. This class provides very similar mutual exclusion features, but it also has the method tryLock, which acquires the lock if it’s free, or returns false immediately if it’s taken.

So you can have something like:

 private final ReentrantLock rlock = new ReentrantLock();

Code of thread 1:

 // thread 1 has normal synchronized behavior
 rlock.lock();
 // code
 rlock.unlock();

And thread 2:

 // thread 2 will skip the code if the lock is already taken
 if(rlock.tryLock()) {
     // code
     rlock.unlock();
 }