com.bluegosling.concurrent.locks

Class NonReentrantLock

java.lang.Object

com.bluegosling.concurrent.locks.NonReentrantLock

All Implemented Interfaces:

Lock

public class NonReentrantLock
extends Object
implements Lock

A non-reentrant lock. It can be created in a fair mode, which ensures FIFO acquisition order, or in an unfair mode (default), which has generally higher throughput. The unfair lock makes a best effort to satisfy acquisitions in FIFO order, but barging can occur (and often will if the lock is highly contended).

Like the name says, this lock is non-reentrant and will deadlock if re-entrance is accidentally attempted.

Since it is not reentrant (i.e. no bookkeeping that allows it to track re-entrance), this lock does not have an exclusive owner thread. This enables patterns of use where it is locked by one thread but then unlocked by another, which facilitates interesting locking protocols that support thread-skips when asynchronous programming styles are used.

Like normal locks, awaiting or signaling a condition requires that the lock be locked. But since the lock has no concept of an "owner", it cannot be verified that it is the awaiting or signaling thread that has locked it.

Awaiting a condition will unlock the lock before parking the awaiting thread. If that unlock operation fails, an IllegalMonitorStateException is thrown. Signaling a condition just does a best effort check that the lock is locked. If the lock is not locked at the onset of the operation, an IllegalMonitorStateException is thrown. But if the lock is concurrently unlocked by another thread, awaiting threads are still signaled.

Constructor Summary

Constructors

Constructor and Description
NonReentrantLock() Constructs a new, unfair lock.
NonReentrantLock(boolean fair) Constructs a new lock.

Method Summary

Modifier and Type	Method and Description
boolean	isFair() Returns true if this is a fair lock.
void	lock()
void	lockInterruptibly()
Condition	newCondition()
boolean	tryLock()
boolean	tryLock(long time, TimeUnit unit)
void	unlock()

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NonReentrantLock

public NonReentrantLock()

Constructs a new, unfair lock.

NonReentrantLock

public NonReentrantLock(boolean fair)

Constructs a new lock.

Parameters:

fair - if true, the new lock is a fair lock; otherwise, it will be unfair

Method Detail

isFair

public boolean isFair()

Returns true if this is a fair lock.

Returns:

true if this is a fair lock

lock

public void lock()

Specified by:

lock in interface Lock

lockInterruptibly

public void lockInterruptibly()
                       throws InterruptedException

Specified by:

lockInterruptibly in interface Lock

Throws:

InterruptedException

tryLock

public boolean tryLock()

Specified by:

tryLock in interface Lock

tryLock

public boolean tryLock(long time,
                       TimeUnit unit)
                throws InterruptedException

Specified by:

tryLock in interface Lock

Throws:

InterruptedException

unlock

public void unlock()

Specified by:

unlock in interface Lock

newCondition

public Condition newCondition()

Specified by:

newCondition in interface Lock