java-design-patterns/event-queue/src/main/java/com/iluwatar/event/queue/Audio.java

/**
 * The MIT License
 * Copyright (c) 2014-2016 Ilkka Seppälä
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package com.iluwatar.event.queue;

import java.io.IOException;

import javax.sound.sampled.AudioInputStream;
import javax.sound.sampled.AudioSystem;
import javax.sound.sampled.Clip;
import javax.sound.sampled.LineUnavailableException;

/**
 * This class implements the Event Queue pattern.
 * @author mkuprivecz
 *
 */
public class Audio {

  private static final int MAX_PENDING = 16;

  private static int headIndex;

  private static int tailIndex;

  private static Thread updateThread = null;

  private static PlayMessage[] pendingAudio = new PlayMessage[MAX_PENDING];

  public static boolean isServiceRunning() {
    return updateThread.isAlive();
  }

  /**
   * This method stops the Update Method's thread. 
   */
  public static void stopService() {
    if (updateThread != null) {
      updateThread.interrupt();
    }
  }

  /**
   * Starts the thread for the Update Method pattern if it was not started previously.
   * Also when the thread is is ready initializes the indexes of the queue 
   */
  public static void init() {
    if (updateThread == null) {
      updateThread = new Thread(new Runnable() {
        public void run() {
          while (!Thread.currentThread().isInterrupted()) {
            Audio.update();
          }
        }
      });
    }
    if (!updateThread.isAlive()) {
      updateThread.start();
      headIndex = 0;
      tailIndex = 0;
    }
  }

  /**
   * This method adds a new audio into the queue.
   * @param stream is the AudioInputStream for the method
   * @param volume is the level of the audio's volume 
   */
  public static void playSound(AudioInputStream stream, float volume) {
    init();
    // Walk the pending requests.
    for (int i = headIndex; i != tailIndex; i = (i + 1) % MAX_PENDING) {
      if (pendingAudio[i].stream == stream) {
        // Use the larger of the two volumes.
        pendingAudio[i].volume = Math.max(volume, pendingAudio[i].volume);

        // Don't need to enqueue.
        return;
      }
    }
    pendingAudio[tailIndex] = new PlayMessage();
    pendingAudio[tailIndex].stream = stream;
    pendingAudio[tailIndex].volume = volume;
    tailIndex = (tailIndex + 1) % MAX_PENDING;
  }
  
  /**
   * This method uses the Update Method pattern.
   * It takes the audio from the queue and plays it
   */
  public static void update() {
    // If there are no pending requests, do nothing.
    if (headIndex == tailIndex) {
      return;
    }
    Clip clip = null;
    try {
      clip = AudioSystem.getClip();
      clip.open(pendingAudio[headIndex].stream);
    } catch (LineUnavailableException e) {
      System.err.println("Error occoured while loading the audio: The line is unavailable");
      e.printStackTrace();
    } catch (IOException e) {
      System.err.println("Input/Output error while loading the audio");
      e.printStackTrace();
    }
    clip.start();

    headIndex++;
  }
}