AsyncExecutor.java

/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 * 
 * 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.badlogic.gdx.utils.async;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;

import com.badlogic.gdx.utils.Disposable;
import com.badlogic.gdx.utils.GdxRuntimeException;

/**
 * Allows asnynchronous execution of {@link AsyncTask} instances on a separate
 * thread. Needs to be disposed via a call to {@link #dispose()} when no longer
 * used, in which case the executor waits for running tasks to finish. Scheduled
 * but not yet running tasks will not be executed.
 * 
 * @author badlogic
 */
public class AsyncExecutor implements Disposable {
    private final ExecutorService executor;

    /**
     * Creates a new AsynchExecutor that allows maxConcurrent {@link Runnable}
     * instances to run in parallel.
     * 
     * @param maxConcurrent
     */
    public AsyncExecutor(int maxConcurrent) {
        executor = Executors.newFixedThreadPool(maxConcurrent, new ThreadFactory() {
            @Override
            public Thread newThread(Runnable r) {
                Thread thread = new Thread(r, "AsynchExecutor-Thread");
                thread.setDaemon(true);
                return thread;
            }
        });
    }

    /**
     * Submits a {@link Runnable} to be executed asynchronously. If
     * maxConcurrent runnables are already running, the runnable will be queued.
     * 
     * @param task
     *            the task to execute asynchronously
     */
    public <T> AsyncResult<T> submit(final AsyncTask<T> task) {
        if (executor.isShutdown()) {
            throw new GdxRuntimeException("Cannot run tasks on an executor that has been shutdown (disposed)");
        }
        return new AsyncResult(executor.submit(new Callable<T>() {
            @Override
            public T call() throws Exception {
                return task.call();
            }
        }));
    }

    /**
     * Waits for running {@link AsyncTask} instances to finish, then destroys
     * any resources like threads. Can not be used after this method is called.
     */
    @Override
    public void dispose() {
        executor.shutdown();
        try {
            executor.awaitTermination(Long.MAX_VALUE, TimeUnit.SECONDS);
        } catch (InterruptedException e) {
            throw new GdxRuntimeException("Couldn't shutdown loading thread", e);
        }
    }
}