Build 1.0_r1(from source)

java.util.concurrent.locks
Class ReentrantReadWriteLock.ReadLock

java.lang.Object
  extended by java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock
All Implemented Interfaces:
Serializable, Lock
Enclosing class:
ReentrantReadWriteLock

public static class ReentrantReadWriteLock.ReadLock
extends Object
implements Lock, Serializable

The lock returned by method ReentrantReadWriteLock.readLock().

See Also:
Serialized Form

Constructor Summary
protected ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock lock)
          Constructor for use by subclasses.
 
Method Summary
 void lock()
          Acquires the shared lock.
 void lockInterruptibly()
          Acquires the shared lock unless the current thread is interrupted.
 Condition newCondition()
          Throws UnsupportedOperationException because ReadLocks do not support conditions.
 String toString()
          Returns a string identifying this lock, as well as its lock state.
 boolean tryLock()
          Acquires the shared lock only if it is not held exclusively by another thread at the time of invocation.
 boolean tryLock(long timeout, TimeUnit unit)
          Acquires the shared lock if it is not held exclusively by another thread within the given waiting time and the current thread has not been interrupted.
 void unlock()
          Attempts to release this lock.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

ReentrantReadWriteLock.ReadLock

protected ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock lock)
Constructor for use by subclasses.

Parameters:
lock - the outer lock object
Throws:
NullPointerException - if lock null
Method Detail

lock

public void lock()
Acquires the shared lock.

Acquires the lock if it is not held exclusively by another thread and returns immediately.

If the lock is held exclusively by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until the lock has been acquired.

Specified by:
lock in interface Lock

lockInterruptibly

public void lockInterruptibly()
                       throws InterruptedException
Acquires the shared lock unless the current thread is interrupted.

Acquires the shared lock if it is not held exclusively by another thread and returns immediately.

If the lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of two things happens:

If the current thread:

then InterruptedException is thrown and the current thread's interrupted status is cleared.

In this implementation, as this method is an explicit interruption point, preference is given to responding to the interrupt over normal or reentrant acquisition of the lock.

Specified by:
lockInterruptibly in interface Lock
Throws:
InterruptedException - if the current thread is interrupted
See Also:
Thread.interrupt()

tryLock

public boolean tryLock()
Acquires the shared lock only if it is not held exclusively by another thread at the time of invocation.

Acquires the lock if it is not held exclusively by another thread and returns immediately with the value true. Even when this lock has been set to use a fair ordering policy, a call to tryLock() will immediately acquire the lock if it is available, whether or not other threads are currently waiting for the lock. This "barging" behavior can be useful in certain circumstances, even though it breaks fairness. If you want to honor the fairness setting for this lock, then use tryLock(0, TimeUnit.SECONDS) which is almost equivalent (it also detects interruption).

If the lock is held exclusively by another thread then this method will return immediately with the value false.

Specified by:
tryLock in interface Lock
Returns:
true if the lock was acquired.

tryLock

public boolean tryLock(long timeout,
                       TimeUnit unit)
                throws InterruptedException
Acquires the shared lock if it is not held exclusively by another thread within the given waiting time and the current thread has not been interrupted.

Acquires the lock if it is not held exclusively by another thread and returns immediately with the value true. If this lock has been set to use a fair ordering policy then an available lock will not be acquired if any other threads are waiting for the lock. This is in contrast to the tryLock() method. If you want a timed tryLock that does permit barging on a fair lock then combine the timed and un-timed forms together:

if (lock.tryLock() || lock.tryLock(timeout, unit) ) { ... }
 

If the lock is held exclusively by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

If the lock is acquired then the value true is returned.

If the current thread:

then InterruptedException is thrown and the current thread's interrupted status is cleared.

If the specified waiting time elapses then the value false is returned. If the time is less than or equal to zero, the method will not wait at all.

In this implementation, as this method is an explicit interruption point, preference is given to responding to the interrupt over normal or reentrant acquisition of the lock, and over reporting the elapse of the waiting time.

Specified by:
tryLock in interface Lock
Parameters:
timeout - the time to wait for the lock
unit - the time unit of the timeout argument
Returns:
true if the lock was acquired.
Throws:
InterruptedException - if the current thread is interrupted
NullPointerException - if unit is null
See Also:
Thread.interrupt()

unlock

public void unlock()
Attempts to release this lock.

If the number of readers is now zero then the lock is made available for other lock attempts.

Specified by:
unlock in interface Lock

newCondition

public Condition newCondition()
Throws UnsupportedOperationException because ReadLocks do not support conditions.

Specified by:
newCondition in interface Lock
Returns:
A new Condition instance for this Lock instance.
Throws:
UnsupportedOperationException - always

toString

public String toString()
Returns a string identifying this lock, as well as its lock state. The state, in brackets, includes the String "Read locks =" followed by the number of held read locks.

Overrides:
toString in class Object
Returns:
a string identifying this lock, as well as its lock state.

Build 1.0_r1(from source)

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