java.util.concurrent.locks
class ReentrantReadWriteLock.ReadLock

java.lang.Object java.util.concurrent.locks.ReentrantReadWriteLock.ReadLock

All Implemented Interfaces:

Serializable, Lock

Enclosing class:

ReentrantReadWriteLock

Most common way to construct:

ReentrantReadWriteLock rwl = …;

ReentrantReadWriteLock.ReadLock l = rwl.readLock();

Based on 37 examples

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

The lock returned by method {@link ReentrantReadWriteLock#readLock}.

ReentrantReadWriteLock.ReadLock

protected ReentrantReadWriteLock.ReadLock(ReentrantReadWriteLock lock)

Constructor for use by subclasses

Parameters:

lock - the outer lock object

lock

public void lock()

Acquires the read lock.

Acquires the read lock if the write lock is not held by another thread and returns immediately.

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

lockInterruptibly

public void lockInterruptibly()
                       throws InterruptedException

Acquires the read lock unless the current thread is {@linkplain Thread#interrupt interrupted}.

Acquires the read lock if the write lock is not held by another thread and returns immediately.

If the write 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:

• The read lock is acquired by the current thread; or
• Some other thread {@linkplain Thread#interrupt interrupts} the current thread.

If the current thread:

• has its interrupted status set on entry to this method; or
• is {@linkplain Thread#interrupt interrupted} while acquiring the read lock,

then {@link 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.

Throws:

InterruptedException - if the current thread is interrupted

newCondition

public Condition newCondition()

Throws {@code UnsupportedOperationException} because {@code ReadLocks} do not support conditions.

toString

public String toString()

Returns a string identifying this lock, as well as its lock state. The state, in brackets, includes the String {@code "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

tryLock

public boolean tryLock()

Acquires the read lock only if the write lock is not held by another thread at the time of invocation.

Acquires the read lock if the write lock is not held by another thread and returns immediately with the value {@code true}. Even when this lock has been set to use a fair ordering policy, a call to {@code tryLock()} will immediately acquire the read lock if it is available, whether or not other threads are currently waiting for the read 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 {@link #tryLock(long, TimeUnit) tryLock(0, TimeUnit.SECONDS) } which is almost equivalent (it also detects interruption).

If the write lock is held by another thread then this method will return immediately with the value {@code false}.

Returns:

{@code true} if the read lock was acquired

tryLock

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

Acquires the read lock if the write lock is not held by another thread within the given waiting time and the current thread has not been {@linkplain Thread#interrupt interrupted}.

Acquires the read lock if the write lock is not held by another thread and returns immediately with the value {@code 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 {@link #tryLock()} method. If you want a timed {@code 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 write lock is held by another thread then the current thread becomes disabled for thread scheduling purposes and lies dormant until one of three things happens:

• The read lock is acquired by the current thread; or
• Some other thread {@linkplain Thread#interrupt interrupts} the current thread; or
• The specified waiting time elapses.

If the read lock is acquired then the value {@code true} is returned.

If the current thread:

• has its interrupted status set on entry to this method; or
• is {@linkplain Thread#interrupt interrupted} while acquiring the read lock,

then {@link InterruptedException} is thrown and the current thread's interrupted status is cleared.

If the specified waiting time elapses then the value {@code 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.

Parameters:

timeout - the time to wait for the read lock

unit - the time unit of the timeout argument

Returns:

{@code true} if the read lock was acquired

Throws:

InterruptedException - if the current thread is interrupted

unlock

public void unlock()

Attempts to release this lock.

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