Question

I know how synchronized methods in java work.

Suppose we have 3 synchronized methods in a class. If a Thread accesses 1 of the available methods, the other 2 get blocked for other threads.

If we change the synchronization implementation in 1 of methods to :

synchronized (this) {...}

Does it still work the same way and block the 2 other methods?

Answer 1

Yes it does.

public synchronized void method() {...}

uses the object’s instrinsic lock (this), so any other synchronized block using that lock:

synchronized(this) {...}

would block if the lock is already held.

Note: if a method is static, the picture is different, because the lock is not this any more, it is YourObject.class. In the example below, nothing prevents a thread T1 to run method while another thread T2 runs someOtherMethod, because the 2 sections don’t use the same lock:

public static synchronized void method() {...}

public void someOtherMethod() {
    synchronized(this) {
    }
}