com.googlecode.concurentlocks.ReadWriteUpdateLock Maven / Gradle / Ivy

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/**
 * Copyright 2013 Niall Gallagher
 *
 * 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 com.googlecode.concurentlocks;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReadWriteLock;

/**
 * Extends the JDK {@link ReadWriteLock}, providing an update lock in addition to the read lock and the write
 * lock.
 * 
 * The {@link #updateLock update lock} supports read-only operations and can coexist with multiple
 * {@link #readLock read lock}s held simultaneously by other reader threads. However it may also be upgraded from
 * its read-only status to a {@link #writeLock write lock}, and it may be downgraded again back to a read lock.
 * 
 * See implementation {@link ReentrantReadWriteUpdateLock} for more details.
 *
 * @author Niall Gallagher
 */
public interface ReadWriteUpdateLock extends ReadWriteLock {

    /**
     * Returns a lock which allows reading and which may also be upgraded to a lock allowing writing.
     *
     * @return a lock which allows reading and which may also be upgraded to a lock allowing writing.
     */
    Lock updateLock();
}