why this synchronized method is not working as expected?

Question

Could someone explain two me why these to codes dont output the same results (the only difference between two codes is in the run() method) ?

NB: the first code seem

Answer 1

When you want to synchronize two threads you must lock on a shared resource by all threads. Synchronizing in the run method(or any instance method in thread class) each thread locks it's own method resulting no synchronization at all.