com.sun.jini.thread

Class ReadersWriter

java.lang.Object

com.sun.jini.thread.ReadersWriter

public class ReadersWriter
extends Object

An Object to control the concurrent state. Allows multiple readers or a single writer. Waiting writers have priority over new readers. Waiting priority writers have priority over waiting regular writers. A single thread cannot hold a lock more than once.

Author:

Sun Microsystems, Inc.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ReadersWriter.ConcurrentLockException InterruptedException transformed to a runtime exception.

Field Summary

Fields

Modifier and Type	Field and Description
private int	activeReaders The number of active readers
private boolean	activeWriter True if there is an active writer
private int	waitingPriorityWriters The number of waiting priority writers
private int	waitingWriters The number of waiting writers (both regular and priority)

Constructor Summary

Constructors

Constructor and Description
ReadersWriter()

Method Summary

Methods

Modifier and Type	Method and Description
void	priorityWriteLock() Obtain a priority write lock.
void	readerWait(Object notifier, long time) Release a read lock, wait the given period of time or until notified by notifier, then obtain a read lock again.
void	readLock() Obtain a read lock.
void	readUnlock() Release a read lock.
void	waiterNotify(Object notifier) Wake up any threads waiting on this notifier.
void	writeLock() Obtain a regular write lock.
void	writerWait(Object notifier, long time) Release a write lock, wait the given period of time or until notified by notifier, then obtain a regular write lock again.
void	writeUnlock() Release a (regular or priority) write lock.

Methods inherited from class java.lang.Object

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

Field Detail

activeReaders

private int activeReaders

The number of active readers

waitingWriters

private int waitingWriters

The number of waiting writers (both regular and priority)

waitingPriorityWriters

private int waitingPriorityWriters

The number of waiting priority writers

activeWriter

private boolean activeWriter

True if there is an active writer

Constructor Detail

ReadersWriter

public ReadersWriter()

Method Detail

readLock

public void readLock()

Obtain a read lock. Multiple concurrent readers allowed.

readUnlock

public void readUnlock()

Release a read lock.

writeLock

public void writeLock()

Obtain a regular write lock. Only a single writer allowed at once.

priorityWriteLock

public void priorityWriteLock()

Obtain a priority write lock. Only a single writer allowed at once.

writeUnlock

public void writeUnlock()

Release a (regular or priority) write lock.

readerWait

public void readerWait(Object notifier,
              long time)

Release a read lock, wait the given period of time or until notified by notifier, then obtain a read lock again. Throws ConcurrentLockException if the thread gets interrupted; in that case, the read lock is still held.

writerWait

public void writerWait(Object notifier,
              long time)

Release a write lock, wait the given period of time or until notified by notifier, then obtain a regular write lock again. Throws ConcurrentLockException if the thread gets interrupted; in that case, the write lock is still held.

waiterNotify

public void waiterNotify(Object notifier)

Wake up any threads waiting on this notifier. In general, because there is no wakeup-waiting flag, this method must be called from a thread that holds a lock that conflicts with the lock that the waiter was holding. If the waiter calls writerWait, then waiterNotify can be called either under a readLock or a writeLock, but if the waiter calls readerWait, then waiterNotify should only be called under a writeLock.