condition variable : Java Glossary

by Roedy Green ©1996-2008 Canadian Mind Products
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condition variable: According to Achim Gratz monitors are insufficient if a thread needs to wait inside a monitor until a condition is met: this thread is inside the monitor and so no other thread can enter and change the condition - a deadlock is the result. Condition variables are used to block a thread inside a monitor (wait()) and allow another thread to enter the monitor. When the condition that has led to the blocking changes this is signalled to blocked threads. Java allows distinction between deblocking a single thread (notify()) and unblocking all threads waiting on the CV (notifyAll()). This feature is of dubious value if not accompanied by additional program logic (you don’t have control over which thread of the wait set gets its turn) and beginners are probably best off using notifyAll() only.
CV
monitor
queue: java.util.concurrent
semaphore
synchronized
Thread
thread safe code

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