Intrinsic Locks

This is Fourth Article in Series of Articles on Java 8 Concurrency Tutorial.

Intrinsic Locks

Synchronization is built around an internal entity known as the intrinsic lock or monitor lock. Intrinsic locks play a role in both aspects of synchronization: enforcing exclusive access to an object’s state and establishing happens-before relationships that are essential to visibility.

Every object has an intrinsic lock associated with it. By convention, a thread that needs exclusive and consistent access to an object’s fields has to acquire the object’s intrinsic lock before accessing them, and then release the intrinsic lock when it’s done with them.

As long as a thread owns an intrinsic lock, no other thread can acquire the same lock. The other thread will block when it attempts to acquire the lock.

Locks In Synchronized Methods

We have discussed Synchronized Methods in previous Article Synchronization.
When a thread invokes a synchronized method, it automatically acquires the intrinsic lock for that method’s object and releases it when the method returns. The lock release occurs even if the return was caused by an uncaught exception.

Locks In Synchronized Static Methods

As a static method is associated with a class, not an object. In this case, the thread acquires the intrinsic lock for the Class object associated with the class. Thus access to class’s static fields is controlled by a lock that’s disti