How Java handle synchronization between threads?
Java provides a few simple structures for synchronizing the activities of threads. They are all based on the concept of monitors, a widely used synchronization scheme developed by C.A.R. Hoare.
A monitor is essentially a lock. The lock is attached to a resource that many threads may need to access, but that should be accessed by only one thread at a time.
In Java, every object has a lock associated with it. To be more specific, every class and every instance of a class has its own lock. The synchronized keyword marks places where a thread must acquire the lock before proceeding.
Often, you want to synchronize multiple methods of the same class, so that only one of the methods modifies or examines parts of the class at a time. All static synchronized methods in a class use the same class object lock. By the same token, all instance methods in a class use the same instance object lock. In this way, Java can guarantee that only one of a set of synchronized methods is running at a time.
In addition to synchronizing entire methods, the synchronized keyword can be used in a special construct to guard arbitrary blocks of code. In this form it also takes an explicit argument that specifies the object for which it is to acquire a lock.
Look at the original post for more information.
Leave a Reply