com.google.common.util.concurrent

Class CycleDetectingLockFactory.WithExplicitOrdering<E extends Enum<E>>

java.lang.Object

com.google.common.util.concurrent.CycleDetectingLockFactory

com.google.common.util.concurrent.CycleDetectingLockFactory.WithExplicitOrdering<E>

Type Parameters:

E - The Enum type representing the explicit lock ordering.

Enclosing class:

CycleDetectingLockFactory

@Beta
public static final class CycleDetectingLockFactory.WithExplicitOrdering<E extends Enum<E>>
extends CycleDetectingLockFactory

A CycleDetectingLockFactory.WithExplicitOrdering provides the additional enforcement of an application-specified ordering of lock acquisitions. The application defines the allowed ordering with an Enum whose values each correspond to a lock type. The order in which the values are declared dictates the allowed order of lock acquisition. In other words, locks corresponding to smaller values of Enum.ordinal() should only be acquired before locks with larger ordinals. Example:

 enum MyLockOrder {
   FIRST, SECOND, THIRD;
 }

 CycleDetectingLockFactory.WithExplicitOrdering<MyLockOrder> factory =
   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(Policies.THROW);

 Lock lock1 = factory.newReentrantLock(MyLockOrder.FIRST);
 Lock lock2 = factory.newReentrantLock(MyLockOrder.SECOND);
 Lock lock3 = factory.newReentrantLock(MyLockOrder.THIRD);

 lock1.lock();
 lock3.lock();
 lock2.lock();  // will throw an IllegalStateException
 

As with all locks created by instances of CycleDetectingLockFactory explicitly ordered locks participate in general cycle detection with all other cycle detecting locks, and a lock's behavior when detecting a cyclic lock acquisition is defined by the Policy of the factory that created it.

Note, however, that although multiple locks can be created for a given Enum value, whether it be through separate factory instances or through multiple calls to the same factory, attempting to acquire multiple locks with the same Enum value (within the same thread) will result in an IllegalStateException regardless of the factory's policy. For example:

 CycleDetectingLockFactory.WithExplicitOrdering<MyLockOrder> factory1 =
   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(...);
 CycleDetectingLockFactory.WithExplicitOrdering<MyLockOrder> factory2 =
   CycleDetectingLockFactory.newInstanceWithExplicitOrdering(...);

 Lock lockA = factory1.newReentrantLock(MyLockOrder.FIRST);
 Lock lockB = factory1.newReentrantLock(MyLockOrder.FIRST);
 Lock lockC = factory2.newReentrantLock(MyLockOrder.FIRST);

 lockA.lock();

 lockB.lock();  // will throw an IllegalStateException
 lockC.lock();  // will throw an IllegalStateException

 lockA.lock();  // reentrant acquisition is okay
 

It is the responsibility of the application to ensure that multiple lock instances with the same rank are never acquired in the same thread.

Since:

13.0

Nested Class Summary

Nested classes/interfaces inherited from class com.google.common.util.concurrent.CycleDetectingLockFactory

CycleDetectingLockFactory.Policies, CycleDetectingLockFactory.Policy, CycleDetectingLockFactory.PotentialDeadlockException, CycleDetectingLockFactory.WithExplicitOrdering<E extends Enum<E>>

Method Summary

Modifier and Type	Method and Description
ReentrantLock	newReentrantLock(E rank) Equivalent to newReentrantLock(rank, false).
ReentrantLock	newReentrantLock(E rank, boolean fair) Creates a ReentrantLock with the given fairness policy and rank.
ReentrantReadWriteLock	newReentrantReadWriteLock(E rank) Equivalent to newReentrantReadWriteLock(rank, false).
ReentrantReadWriteLock	newReentrantReadWriteLock(E rank, boolean fair) Creates a ReentrantReadWriteLock with the given fairness policy and rank.

Methods inherited from class com.google.common.util.concurrent.CycleDetectingLockFactory

newInstance, newInstanceWithExplicitOrdering, newReentrantLock, newReentrantLock, newReentrantReadWriteLock, newReentrantReadWriteLock

Methods inherited from class java.lang.Object

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

Method Detail

newReentrantLock

public ReentrantLock newReentrantLock(E rank)

Equivalent to newReentrantLock(rank, false).

newReentrantLock

public ReentrantLock newReentrantLock(E rank,
                                      boolean fair)

Creates a ReentrantLock with the given fairness policy and rank. The values returned by Enum.getDeclaringClass() and Enum.name() are used to describe the lock in warning or exception output.

Throws:

IllegalStateException - If the factory has already created a Lock with the specified rank.

newReentrantReadWriteLock

public ReentrantReadWriteLock newReentrantReadWriteLock(E rank)

Equivalent to newReentrantReadWriteLock(rank, false).

newReentrantReadWriteLock

public ReentrantReadWriteLock newReentrantReadWriteLock(E rank,
                                                        boolean fair)

Creates a ReentrantReadWriteLock with the given fairness policy and rank. The values returned by Enum.getDeclaringClass() and Enum.name() are used to describe the lock in warning or exception output.

Throws:

IllegalStateException - If the factory has already created a Lock with the specified rank.