Java Glossary : monitor

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monitor: Java uses monitors to co-ordinate threads to make sure they don't trip over each other accessing the same data. With monitors, you either lock objects, critical sections of code or you lock entire methods by declaring them synchronised. Monitors have hardware test and set support behind them to ensure a thread checks to see if a monitor is already locked and if not, seize the lock all in one non-interruptible atomic operation. Without atomicity, a thread might check see if the monitor is unlocked, and have some other thread grab the monitor before it gets a chance to lock it. Purists will point out that a monitor is not actually the lock, but rather the way that lock is used to protect critical sections of code.
condition variable ¤ mutex ¤ semaphore ¤ Thread synchronized

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