/*
* Copyright 2005 the original author or authors.
- *
+ *
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
- *
+ *
* http://www.apache.org/licenses/LICENSE-2.0
- *
+ *
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
- */
+ */
package org.wamblee.concurrency;
import java.util.HashSet;
-
/**
* Read-write lock for allowing multiple concurrent readers or at most one
* writer. This implementation does not aim for high performance but for
*/
public class ReadWriteLock {
/**
- * Sets containing the references to the threads that are currently
- * reading. This administration is useful to check that the lock has
- * already been acquired before it is release. This check adds robustness
- * to the application.
+ * Sets containing the references to the threads that are currently reading.
+ * This administration is useful to check that the lock has already been
+ * acquired before it is release. This check adds robustness to the
+ * application.
*/
private HashSet<Thread> readers;
* Constructs read-write lock.
*/
public ReadWriteLock() {
- readers = new HashSet<Thread>();
- writer = null;
+ readers = new HashSet<Thread>();
+ writer = null;
}
/**
- * Acquires the lock for reading. This call will block until the lock can
- * be acquired.
- *
- * @throws IllegalStateException Thrown if the read or write lock is
- * already acquired.
+ * Acquires the lock for reading. This call will block until the lock can be
+ * acquired.
+ *
+ * @throws IllegalStateException
+ * Thrown if the read or write lock is already acquired.
*/
public synchronized void acquireRead() {
if (readers.contains(Thread.currentThread())) {
throw new IllegalStateException(
- "Read lock already acquired by current thread: "
- + Thread.currentThread());
+ "Read lock already acquired by current thread: " +
+ Thread.currentThread());
}
if (writer == Thread.currentThread()) {
throw new IllegalStateException(
- "Trying to acquire the read lock while already holding a write lock: "
- + Thread.currentThread());
+ "Trying to acquire the read lock while already holding a write lock: " +
+ Thread.currentThread());
}
while (writer != null) {
}
/**
- * Releases the lock for reading. Note: This implementation assumes that
- * the lock has already been acquired for reading previously.
- *
- * @throws IllegalStateException Thrown when the lock was not acquired by
- * this thread.
+ * Releases the lock for reading. Note: This implementation assumes that the
+ * lock has already been acquired for reading previously.
+ *
+ * @throws IllegalStateException
+ * Thrown when the lock was not acquired by this thread.
*/
public synchronized void releaseRead() {
if (!readers.remove(Thread.currentThread())) {
/**
* Acquires the lock for writing. This call will block until the lock has
* been acquired.
- *
- * @throws IllegalStateException Thrown if the read or write lock is
- * already acquired.
+ *
+ * @throws IllegalStateException
+ * Thrown if the read or write lock is already acquired.
*/
public synchronized void acquireWrite() {
if (writer == Thread.currentThread()) {
throw new IllegalStateException(
- "Trying to acquire a write lock while already holding the write lock: "
- + Thread.currentThread());
+ "Trying to acquire a write lock while already holding the write lock: " +
+ Thread.currentThread());
}
if (readers.contains(Thread.currentThread())) {
throw new IllegalStateException(
- "Trying to acquire a write lock while already holding the read lock: "
- + Thread.currentThread());
+ "Trying to acquire a write lock while already holding the read lock: " +
+ Thread.currentThread());
}
// wait until there are no more writers and no more
- // readers
+ // readers
while ((writer != null) || (readers.size() > 0)) {
try {
wait();
/**
* Releases the lock for writing.
- *
- * @throws IllegalStateException Thrown when the lock was not acquired.
+ *
+ * @throws IllegalStateException
+ * Thrown when the lock was not acquired.
*/
public synchronized void releaseWrite() {
if (writer != Thread.currentThread()) {
git://wamblee.org / utils / blobdiff