Synchronization in case of Inheritance in java

Question

Suppose there are 2 classes, Parent class and Child class which extends Parent class. Now and both have two method which are synchronized.My question which object lock will be use for locking this synchronized methods i create object like : Parent p=new Child(); Is is parent object lock or Child object lock?

Answer 1

There is no parent object lock or child object lock. There is only one lock, the object's. In this case, it will be p's.

Threads will block when entering a parent's synchronized method if another thread has the lock in a child's synchronized method, and vice versa.