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Groovy example source code file (LockableObject.java)

This example Groovy source code file (LockableObject.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Groovy tags/keywords

abstractqueuedsynchronizer, abstractqueuedsynchronizer, illegalmonitorstateexception, illegalmonitorstateexception, lockableobject, lockableobject, thread, thread

The Groovy LockableObject.java source code

/*
 * Copyright 2003-2010 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.codehaus.groovy.util;

import java.util.concurrent.locks.AbstractQueuedSynchronizer;

/**
 * A bit simplified lock designed to be inherited by.
 */
public class LockableObject extends AbstractQueuedSynchronizer {
    transient Thread owner;

    protected final boolean isHeldExclusively() {
        return getState() != 0 && owner == Thread.currentThread();
    }

    public final void lock() {
        if (compareAndSetState(0, 1))
            owner = Thread.currentThread();
        else
            acquire(1);
    }

    public final void unlock() {
        release(1);
    }

    protected final boolean tryAcquire(int acquires) {
        final Thread current = Thread.currentThread();
        int c = getState();
        if (c == 0) {
            if (compareAndSetState(0, acquires)) {
                owner = current;
                return true;
            }
        }
        else if (current == owner) {
            setState(c+ acquires);
            return true;
        }
        return false;
    }

    protected final boolean tryRelease(int releases) {
        int c = getState() - releases;
        if (Thread.currentThread() != owner)
            throw new IllegalMonitorStateException();
        boolean free = false;
        if (c == 0) {
            free = true;
            owner = null;
        }
        setState(c);
        return free;
    }
}

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