synchronized block for an Integer object

Question

I just came across the synchronized block in Java and wrote a small programm to test how it works.

I create 10 threads and let each thread increment an Integer objec

Answer 1

As assumed it is because of the immutability of the Integer object.

I've changed the synchonized block to

Integer old = syncObj;
syncObj ++;
System.out.println(syncObj == old);

and my console gets filled with falses

So each time I increment the Integer a new object is createt.

Therefore I only read from the old Object and it will not be locked.