Java线程教程

Question

I'm looking through the Java concurrency tutorials to get an idea of how this works in Java and had a question regarding the "MsLunch" example @ http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html

I'm trying to understand in the MsLunch example, the difference between coding it as shown, and using 2 synchronized methods.

From what I can understand, using the synchronized keyword on methods relies on an instrinic lock associated with that methods object. So if a class has two synchronized methods a() and b() , a() and b() cannot be called concurrently on the same object.

But coding a() and b() as shown in the MsLunch class allows both methods to be called on the same object at the same time.

Is my understanding correct?

Answer 1

MsLunch example uses synchronized blocks with different object instances to lock. Hence both inc1() and inc2() can run concurrently.

If it were synchronized methods, in that case this will be used to lock, methods inc1() and inc2() would be executed serially.

Answer 2

在http://docs.oracle.com/javase/tutorial/essential/concurrency/locksync.html中， MSLunch具有Sync块，而不是在两个不同的锁上都具有同步方法，因此，是的，两个线程将不会相互阻塞，并且能够同时访问方法。