Java Concurrency - (Object) Wait
Table of Contents
1 - About
Process / Thread - Waiting state in Java.
Object.wait, wait(long timeout) and wait(long timeout, int nanos) suspend the current thread.
The invocation of wait does not return until another thread has issued a notification that some special event may have occurred — though not necessarily the event this thread is waiting for.
When wait is invoked, the thread releases the lock and suspends execution.
2 - Articles Related
3 - Set
Every object has a wait set of threads.
4 - Syntax
public synchronized void guardedJoy() {
// This guard only loops once for each special event, which may not
// be the event we're waiting for.
while(!joy) {
try {
wait();
} catch (InterruptedException e) {}
}
System.out.println("Joy and efficiency have been achieved!");
}
Always invoke wait inside a loop that tests for the condition being waited for. Don't assume that the interrupt was for the particular condition you were waiting for, or that the condition is still true.
5 - Notification
- Object.notifyAll, informing all threads waiting on that lock that something important has happened.
- Object.notify wakes up arbitrary a single thread. Because notify doesn't allow you to specify the thread that is woken up, it is useful only in massively parallel applications — that is, programs with a large number of threads, all doing similar chores. In such an application, you don't care which thread gets woken up.