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Reentrant Lock in Java:

A reference to explicit locking, fairness, timed acquisition, and conditions with ReentrantLock.

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  • Reentrant: Thread can reacquire lock, incrementing hold count.
  • Explicit Lock/Unlock: Uses lock() and unlock(), typically in try-finally.
  • Fairness: Optional fair mode (new ReentrantLock(true)) reduces starvation.
  • TryLock: Non-blocking tryLock() or timed tryLock(long, TimeUnit).
  • Conditions: Supports multiple Condition objects for thread coordination.
  • Interruptible: lockInterruptibly() allows interruption during lock wait.
  • Hold Count: Tracks reentrant acquisitions with getHoldCount().
  • Ownership: Checks lock owner (getOwner()) or current thread (isHeldByCurrentThread()).
  • Queue Info: Inspects waiting threads with getQueueLength() or getWaitingThreads().
  • Flexible Scope: Lock/unlock not bound to block scope.
  • High Performance: Often outperforms synchronized in contention.
  • No Deadlock Prevention: Requires careful use to avoid deadlocks.

Also see.

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