A Reader/Writer lock originally written for ICU service implementation. The internal implementation was replaced with the JDK's stock read write lock (ReentrantReadWriteLock) for ICU 52.

This assumes that there will be little writing contention. It also doesn't allow active readers to acquire and release a write lock, or deal with priority inversion issues.

Access to the lock should be enclosed in a try/finally block in order to ensure that the lock is always released in case of exceptions:

try {
    lock.acquireRead();
    // use service protected by the lock
}
finally {
    lock.releaseRead();
}

The lock provides utility methods getStats and clearStats to return statistics on the use of the lock.

Nested and Inner Type Summary

Modifier and Type	Class and Description
public static class	ICURWLock.Stats Internal class used to gather statistics on the RWLock.

Modifier and Type	Field and Description
private ReentrantReadWriteLock	rwl
private ICURWLock.Stats	stats

Constructor Summary

Access	Constructor and Description
public	ICURWLock()

Method Summary

Modifier and Type	Method and Description
public void	acquireRead() Acquire a read lock, blocking until a read lock is available.
public void	acquireWrite() Acquire the write lock, blocking until the write lock is available.
public synchronized ICURWLock.Stats	clearStats() Clear the stats (stop collecting stats).
public synchronized ICURWLock.Stats	getStats() Return a snapshot of the current stats.
public void	releaseRead() Release a read lock and return.
public void	releaseWrite() Release the write lock and return.
public synchronized ICURWLock.Stats	resetStats() Reset the stats.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll toString wait wait wait

rwl	back to summary
private ReentrantReadWriteLock rwl

stats	back to summary
private ICURWLock.Stats stats

Constructor Detail

ICURWLock	back to summary
public ICURWLock()

Method Detail

acquireRead	back to summary
public void acquireRead() Acquire a read lock, blocking until a read lock is available. Multiple readers can concurrently hold the read lock. If there's a writer, or a waiting writer, increment the waiting reader count and block on this. Otherwise increment the active reader count and return. Caller must call releaseRead when done (for example, in a finally block).

acquireRead

back to summary

public void acquireRead()

Acquire a read lock, blocking until a read lock is available. Multiple readers can concurrently hold the read lock.

If there's a writer, or a waiting writer, increment the waiting reader count and block on this. Otherwise increment the active reader count and return. Caller must call releaseRead when done (for example, in a finally block).

acquireWrite	back to summary
public void acquireWrite() Acquire the write lock, blocking until the write lock is available. Only one writer can acquire the write lock, and when held, no readers can acquire the read lock. If there are no readers and no waiting writers, mark as having an active writer and return. Otherwise, add a lock to the end of the waiting writer list, and block on it. Caller must call releaseWrite when done (for example, in a finally block).

acquireWrite

back to summary

public void acquireWrite()

Acquire the write lock, blocking until the write lock is available. Only one writer can acquire the write lock, and when held, no readers can acquire the read lock.

If there are no readers and no waiting writers, mark as having an active writer and return. Otherwise, add a lock to the end of the waiting writer list, and block on it. Caller must call releaseWrite when done (for example, in a finally block).

clearStats	back to summary
public synchronized ICURWLock.Stats clearStats() Clear the stats (stop collecting stats). Returns existing stats, if any.

getStats	back to summary
public synchronized ICURWLock.Stats getStats() Return a snapshot of the current stats. This does not reset the stats.

releaseRead	back to summary
public void releaseRead() Release a read lock and return. An error will be thrown if a read lock is not currently held. If this is the last active reader, notify the oldest waiting writer. Call when finished with work controlled by acquireRead.

releaseRead

back to summary

public void releaseRead()

Release a read lock and return. An error will be thrown if a read lock is not currently held.

If this is the last active reader, notify the oldest waiting writer. Call when finished with work controlled by acquireRead.

releaseWrite	back to summary
public void releaseWrite() Release the write lock and return. An error will be thrown if the write lock is not currently held. If there are waiting readers, make them all active and notify all of them. Otherwise, notify the oldest waiting writer, if any. Call when finished with work controlled by acquireWrite.

releaseWrite

back to summary

public void releaseWrite()

Release the write lock and return. An error will be thrown if the write lock is not currently held.

If there are waiting readers, make them all active and notify all of them. Otherwise, notify the oldest waiting writer, if any. Call when finished with work controlled by acquireWrite.

resetStats	back to summary
public synchronized ICURWLock.Stats resetStats() Reset the stats. Returns existing stats, if any.

com.ibm.icu.impl back to summary

public final Class ICURWLock.Stats

Class Inheritance

extends Object

java.lang.Object
com.ibm.icu.impl.ICURWLock.Stats

Internal class used to gather statistics on the RWLock.

Field Summary

Modifier and Type	Field and Description
public int	_mrc Number of times concurrent read access granted (multiple read count).
public int	_rc Number of times read access granted (read count).
public int	_wc Number of times write access granted (writer count).
public int	_wrc Number of times blocked for read (waiting reader count).
public int	_wwc Number of times blocked for write (waiting writer count).

Constructor Summary

Access	Constructor and Description
private	Stats()
private	Stats(int rc, int mrc, int wrc, int wc, int wwc)
private	Stats(ICURWLock.Stats rhs)

Method Summary

Modifier and Type	Method and Description
public String	toString() Overrides java.lang.Object.toString. Return a string listing all the stats.

Inherited from java.lang.Object:: clone equals finalize getClass hashCode notify notifyAll wait wait wait

Field Detail

_mrc	back to summary
public int _mrc Number of times concurrent read access granted (multiple read count).

_rc	back to summary
public int _rc Number of times read access granted (read count).

_wc	back to summary
public int _wc Number of times write access granted (writer count).

_wrc	back to summary
public int _wrc Number of times blocked for read (waiting reader count).

_wwc	back to summary
public int _wwc Number of times blocked for write (waiting writer count).

Constructor Detail

Stats	back to summary
private Stats()

Stats	back to summary
private Stats(int rc, int mrc, int wrc, int wc, int wwc)

Stats	back to summary
private Stats(ICURWLock.Stats rhs)

Method Detail

toString	back to summary
public String toString() Overrides java.lang.Object.toString. Return a string listing all the stats. Returns:String Doc from java.lang.Object.toString. a string representation of the object. Annotations @Override

public Class ICURWLock

Nested and Inner Type Summary

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail

public final Class ICURWLock.Stats

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail