org.cache2k.core.concurrency

Interface OptimisticLock

All Known Implementing Classes:

NonOptimisticLock, OptimisticLockStamped

public interface OptimisticLock

Interface for a lock that allows an optimistic read by comparing a stamp value. The basic interface is identical to the Java 8 StampedLock

The implementation may support optimistic locking if available at the platform. If not supported, validate(long) returns always false. This allows the identical usage pattern for both variants.

Author:

Jens Wilke

Method Summary

Modifier and Type	Method and Description
long	readLock() Non-exclusively acquires the lock, blocking if necessary until available.
long	tryOptimisticRead() Returns a stamp that can later be validated, or zero if exclusively locked.
void	unlockRead(long stamp) If the lock state matches the given stamp, releases the non-exclusive lock.
void	unlockWrite(long stamp) If the lock state matches the given stamp, releases the exclusive lock.
boolean	validate(long stamp) Returns true if the lock has not been exclusively acquired since issuance of the given stamp.
long	writeLock() Exclusively acquires the lock, blocking if necessary until available.

Method Detail

writeLock

long writeLock()

Exclusively acquires the lock, blocking if necessary until available.

Returns:

a stamp that can be used to unlock or convert mode

readLock

long readLock()

Non-exclusively acquires the lock, blocking if necessary until available.

Returns:

a stamp that can be used to unlock or convert mode

tryOptimisticRead

long tryOptimisticRead()

Returns a stamp that can later be validated, or zero if exclusively locked. Also ensures that all stores that happened before unlockWrite(long) become visible.

Returns:

a stamp, or zero if exclusively locked

validate

boolean validate(long stamp)

Returns true if the lock has not been exclusively acquired since issuance of the given stamp. Always returns false if the stamp is zero. Always returns true if the stamp represents a currently held lock. Invoking this method with a value not obtained from tryOptimisticRead() or a locking method for this lock has no defined effect or result.

Parameters:

stamp - a stamp

Returns:

true if the lock has not been exclusively acquired since issuance of the given stamp; else false

unlockRead

void unlockRead(long stamp)

If the lock state matches the given stamp, releases the non-exclusive lock.

Parameters:

stamp - a stamp returned by a read-lock operation

Throws:

IllegalMonitorStateException - if the stamp does not match the current state of this lock

unlockWrite

void unlockWrite(long stamp)

If the lock state matches the given stamp, releases the exclusive lock.

Parameters:

stamp - a stamp returned by a write-lock operation

Throws:

IllegalMonitorStateException - if the stamp does not match the current state of this lock