de.aristaflow.adept2.util.locking

Class ReentrantLock.Lock

java.lang.Object

de.aristaflow.adept2.util.locking.ReentrantLock.Lock

Direct Known Subclasses:

ReentrantLock.ReadLock, ReentrantLock.WriteLock

Enclosing class:

ReentrantLock<T>

public class ReentrantLock.Lock
extends java.lang.Object

Represents a reentrant exclusive lock which allows only one object to hold the lock but it may hold it multiple times.

Author:

Ulrich Kreher

Field Summary

Fields

Modifier and Type	Field and Description
protected LockCountManager<? super T>	lockCountManager The manager for counting the lock acquisitions of an object and encapsulating whether objects are equal.
protected java.util.concurrent.atomic.AtomicInteger	waitersForLock Counts how many threads are waiting to get this lock.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	Lock(LockCountManager<? super T> lockCountManager) Creates a new exclusive lock using the designated LockCountManager for comparing objects.

Method Summary

Modifier and Type	Method and Description
java.lang.String	currentLockingObject() Retrieves a string representation of the object that is currently holding the lock.
boolean	hasLock(T object) Determines if the designated object holds this lock.
boolean	isLocked() Returns whether this lock is currently locked by at least one object.
void	lock(T object) Provides the designated object with an exclusive lock.
void	lock(T object, long timeout) Provides the designated object with an exclusive lock.
protected boolean	notificationRequired() Gets whether a notification of waiting threads is required.
int	objectsWaitingToLock() Returns the number of objects waiting to acquire this lock.
boolean	unlock(T object) Releases this lock for the designated object if it holds the lock.

Methods inherited from class java.lang.Object

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

Field Detail

lockCountManager

protected final LockCountManager<? super T> lockCountManager

The manager for counting the lock acquisitions of an object and encapsulating whether objects are equal.

waitersForLock

protected final java.util.concurrent.atomic.AtomicInteger waitersForLock

Counts how many threads are waiting to get this lock.

Constructor Detail

Lock

protected Lock(LockCountManager<? super T> lockCountManager)

Creates a new exclusive lock using the designated LockCountManager for comparing objects.

Parameters:

lockCountManager - The manager counting locks for objects.

Method Detail

lock

public void lock(T object)
          throws java.lang.InterruptedException

Provides the designated object with an exclusive lock. The current thread will be blocked until the lock can be acquired.

Calls Lock.lock(object, 0).

Parameters:

object - The object that requests an exclusive lock.

Throws:

java.lang.InterruptedException - If the thread is interrupted while waiting for the lock, an InterruptedException will be thrown.

lock

public void lock(T object,
                 long timeout)
          throws java.lang.InterruptedException,
                 java.util.concurrent.TimeoutException

Provides the designated object with an exclusive lock. The current thread will be blocked until the lock can be acquired or the timeout elapsed.

Since the lock is reentrant, an object may acquire a lock multiple times. But it also has to release the lock per acquisition afterwards.

Parameters:

object - The object that requests an exclusive lock.

timeout - The time to wait for the lock. A timeout <= 0 means to wait forever (or until the lock is granted).

Throws:

java.lang.InterruptedException - If the thread is interrupted while waiting for the lock, an InterruptedException will be thrown.

java.util.concurrent.TimeoutException - If the designated timeout elapsed before the lock can be acquired, a TimeoutException will be thrown.

hasLock

public boolean hasLock(T object)

Determines if the designated object holds this lock.

Parameters:

object - The object that should be checked to hold this lock.

Returns:

Whether the designated object holds this lock.

isLocked

public boolean isLocked()

Returns whether this lock is currently locked by at least one object.

Returns:

Whether this lock is currently locked by at least one object.

objectsWaitingToLock

public int objectsWaitingToLock()

Returns the number of objects waiting to acquire this lock.

Returns:

The number of objects waiting to acquire this lock

unlock

public boolean unlock(T object)

Releases this lock for the designated object if it holds the lock. If there are other objects waiting for this lock, they will be notified.

Parameters:

object - The object for which the lock should be released.

Returns:

Whether a notification is sent. This will be done only if the lock is available now and there are already other objects waiting for this lock. Otherwise (the lock remains locked by another object or it is available but there are no waiters for it) false will be returned.

Throws:

java.lang.IllegalArgumentException - If the designated object does not hold this lock, an IllegalArgumentException will be thrown.

notificationRequired

protected boolean notificationRequired()

Gets whether a notification of waiting threads is required. This depends on whether there are no more locks and whether there are threads waiting for the lock.

Returns:

Whether a notification of waiting threads is required (no more locks and there are waiters for the lock).

currentLockingObject

public java.lang.String currentLockingObject()

Retrieves a string representation of the object that is currently holding the lock. Due to security reasons the object may not be returned since this would allow to unlock.

Returns:

A string representation of the current (or one in case of several) locking objects; the empty string will be returned, if the lock is not locked.