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jMonkeyEngine is a 3-D game engine for adventurous Java developers
There is a newer version: 3.7.0-stable
/*
 * Copyright (c) 2009-2020 jMonkeyEngine
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'jMonkeyEngine' nor the names of its contributors
 *   may be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package com.jme3.app;

import java.util.concurrent.*;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;
import java.util.logging.Level;
import java.util.logging.Logger;

/**
 * AppTask is used in AppTaskQueue to manage tasks that have
 * yet to be accomplished. The AppTask system is used to execute tasks either
 * in the OpenGL/Render thread, or outside of it.
 *
 * @author Matthew D. Hicks, lazloh
 */
public class AppTask implements Future {
    private static final Logger logger = Logger.getLogger(AppTask.class
            .getName());

    private final Callable callable;

    private V result;
    private ExecutionException exception;
    private boolean cancelled, finished;
    private final ReentrantLock stateLock = new ReentrantLock();
    private final Condition finishedCondition = stateLock.newCondition();

    /**
     * Create an AppTask that will execute the given 
     * {@link Callable}.
     * 
     * @param callable The callable to be executed
     */
    public AppTask(Callable callable) {
        this.callable = callable;
    }

    @Override
    public boolean cancel(boolean mayInterruptIfRunning) {
        stateLock.lock();
        try {
            if (result != null) {
                return false;
            }
            cancelled = true;

            finishedCondition.signalAll();

            return true;
        } finally {
            stateLock.unlock();
        }
    }

    @Override
    public V get() throws InterruptedException, ExecutionException {
        stateLock.lock();
        try {
            while (!isDone()) {
                finishedCondition.await();
            }
            if (exception != null) {
                throw exception;
            }
            return result;
        } finally {
            stateLock.unlock();
        }
    }

    @Override
    public V get(long timeout, TimeUnit unit) throws InterruptedException, ExecutionException, TimeoutException {
        stateLock.lock();
        try {
            if (!isDone()) {
                finishedCondition.await(timeout, unit);
            }
            if (exception != null) {
                throw exception;
            }
            if (result == null) {
                throw new TimeoutException("Object not returned in time allocated.");
            }
            return result;
        } finally {
            stateLock.unlock();
        }
    }

    @Override
    public boolean isCancelled() {
        stateLock.lock();
        try {
            return cancelled;
        } finally {
            stateLock.unlock();
        }
    }

    @Override
    public boolean isDone() {
        stateLock.lock();
        try {
            return finished || cancelled || (exception != null);
        } finally {
            stateLock.unlock();
        }
    }

    public Callable getCallable() {
        return callable;
    }

    public void invoke() {
        try {
            final V tmpResult = callable.call();

            stateLock.lock();
            try {
                result = tmpResult;
                finished = true;

                finishedCondition.signalAll();
            } finally {
                stateLock.unlock();
            }
        } catch (Exception e) {
            logger.logp(Level.SEVERE, this.getClass().toString(), "invoke()", "Exception", e);

            stateLock.lock();
            try {
                exception = new ExecutionException(e);

                finishedCondition.signalAll();
            } finally {
                stateLock.unlock();
            }
        }
    }

}