How do I use thread wait and notify?

How do I use thread wait and notify?

There are two ways of notifying waiting threads.

1. 4.1. notify() For all threads waiting on this object’s monitor (by using any one of the wait() methods), the method notify() notifies any one of them to wake up arbitrarily.
2. 4.2. notifyAll() This method simply wakes all threads that are waiting on this object’s monitor.

Why do we need the wait () and notify () methods?

We wait on an object if we are waiting for some condition to change – some resource to become available. We notify on an object if we want to awaken sleeping threads. There can be any number of lock objects in your program – each locking a particular resource or code segment.

Does notify all release lock?

No — notify / notifyAll don’t release locks like wait does. The awakened thread can’t run until the code which called notify releases its lock. The thread then waits until it can re-obtain ownership of the monitor and resumes execution.

Which method is used to notify all the threads which are waiting for a lock?

The notifyAll() method wakes up all threads waiting on an object lock and allows threads whose condition predicate is true to resume execution.

Is it possible to call the wait method in a non Synchronised block?

If you need to call wait(), notify(), or notifyAll() from within a non-synchronized method, then you must first obtain a lock on the object’s monitor. If you don’t, an exception will be generated when an attempt is made to call the method in question. Now when the methods are called no exception is thrown.

Does wait method release lock?

Thread inside the synchronized method is set as the owner of the lock and is in RUNNABLE state. Any thread that attempts to enter the locked method becomes BLOCKED. When thread calls wait it releases the current object lock (it keeps all locks from other objects) and than goes to WAITING state.

How to notify all waiting threads in Java?

There are two ways of notifying waiting threads. For all threads waiting on this object’s monitor (by using any one of the wait () method), the method notify () notifies any one of them to wake up arbitrarily. The choice of exactly which thread to wake is non-deterministic and depends upon the implementation.

Why does notifyAll Wake Up All the threads in the wait set?

Of course notifyAll wakes up all the threads in the wait set, but again that is something the lock and the scheduler know. The thread calling notifyAll doesn’t know about what threads are waiting. The system is designed intentionally so that threads cannot notify other threads directly.

What’s the difference between join and wait in multithreading?

I have not worked in multithreading, what is the difference between join and wait ,notify method ? is the difference only limited to obtain lock and refrain other threads from accessing it or are there other use cases? Why should I go for wait and notify in multithreading when join can be used for completion of thread execution?

When to use notifyAll instead of wait and notify?

Use notifyAll instead of notify if you expect that more than one thread will be waiting for a lock. The wait and notify methods must be called in a synchronized context. See the link for a more detailed explanation.