Inter-thread
communication: It is all about allowing synchronized
threads to communicate with each other. It is a mechanism in which a thread is
paused running in its critical section and another thread is allowed to enter
(or lock) in the same critical section to be executed.It is implemented by
following methods of Object class.
a. wait() b. notify() c. notifyAll()
wait(): It Causes
current thread to release the lock and wait until either another thread invokes
the notify() method or the notifyAll() method for this object, or a specified
amount of time has elapsed. The notify() is used to unblock one waiting thread
whereas notifyAll() method is used to unblock all the threads in waiting state.
The current thread must own this object's monitor, so it must be called from the synchronized method only otherwise it will throw exception
The current thread must own this object's monitor, so it must be called from the synchronized method only otherwise it will throw exception
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S.No
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Method
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Description
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1
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public
final void wait()throws InterruptedException
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waits
until object is notified
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2
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public
final void wait(long timeout)throws InterruptedException
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waits for
the specified amount of time
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Syntax: public final void notify()
notifyAll(): Wakes up all threads that are waiting on this object's monitor.
Syntax:
public final void notifyAll()
Note: Above 3 methods are in object class because they are related to
lock and object has a lock.
Explanation of Inter
thread Communication:
The point to point explanation of the above diagram is as follows:
1. Threads enter to acquire lock.
2. Lock is acquired by on thread.
3. Now thread goes to waiting state if you call wait() method on the object. Otherwise it releases the lock and exits.
4. If you call notify() or notifyAll() method, thread moves to the notified state (runnable state).
5. Now thread is available to acquire lock.
6. After completion of the task, thread releases the lock and exits the monitor state of the object.
The point to point explanation of the above diagram is as follows:
1. Threads enter to acquire lock.
2. Lock is acquired by on thread.
3. Now thread goes to waiting state if you call wait() method on the object. Otherwise it releases the lock and exits.
4. If you call notify() or notifyAll() method, thread moves to the notified state (runnable state).
5. Now thread is available to acquire lock.
6. After completion of the task, thread releases the lock and exits the monitor state of the object.
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