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‎event-queue/README.md‎

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‎event-queue/etc/Bass-Drum-1.wav‎

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‎event-queue/etc/Closed-Hi-Hat-1.wav‎

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‎event-queue/pom.xml‎

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<?xml version="1.0"?>
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<!--
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The MIT License
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Copyright (c) 2014-2016 Ilkka Seppälä
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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THE SOFTWARE.
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-->
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<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd" xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>com.iluwatar</groupId>
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<artifactId>java-design-patterns</artifactId>
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<version>1.16.0-SNAPSHOT</version>
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</parent>
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<artifactId>event-queue</artifactId>
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<dependencies>
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎event-queue/src/main/java/com/iluwatar/event/queue/App.java‎

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.event.queue;
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import java.io.BufferedReader;
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import java.io.File;
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import java.io.IOException;
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import java.io.InputStreamReader;
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import javax.sound.sampled.AudioInputStream;
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import javax.sound.sampled.AudioSystem;
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import javax.sound.sampled.UnsupportedAudioFileException;
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/**
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* Event or message queues provide an asynchronous communications protocol, meaning that the sender
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* and receiver of the message do not need to interact with the message queue at the same time.
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* Events or messages placed onto the queue are stored until the recipient retrieves them. Event
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* or message queues have implicit or explicit limits on the size of data that may be transmitted
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* in a single message and the number of messages that may remain outstanding on the queue.
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* A queue stores a series of notifications or requests in first-in, first-out order.
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* Sending a notification enqueues the request and returns. The request processor then processes
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* items from the queue at a later time.
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*/
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public class App {
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/**
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* Program entry point.
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*
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* @param args command line args
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* @throws IOException when there is a problem with the audio file loading
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* @throws UnsupportedAudioFileException when the loaded audio file is unsupported
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*/
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public static void main(String[] args) throws UnsupportedAudioFileException, IOException {
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Audio.playSound(getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
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Audio.playSound(getAudioStream("./etc/Closed-Hi-Hat-1.wav"), -8.0f);
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System.out.println("Press Enter key to stop the program...");
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BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
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br.read();
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Audio.stopService();
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}
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public static AudioInputStream getAudioStream(String filePath)
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throws UnsupportedAudioFileException, IOException {
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return AudioSystem.getAudioInputStream(new File(filePath).getAbsoluteFile());
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}
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}

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

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/**
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* The MIT License
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* Copyright (c) 2014-2016 Ilkka Seppälä
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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package com.iluwatar.event.queue;
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import java.io.IOException;
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import javax.sound.sampled.AudioInputStream;
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import javax.sound.sampled.AudioSystem;
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import javax.sound.sampled.Clip;
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import javax.sound.sampled.LineUnavailableException;
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/**
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* This class implements the Event Queue pattern.
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* @author mkuprivecz
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*
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*/
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public class Audio {
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private static final int MAX_PENDING = 16;
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private static int headIndex;
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private static int tailIndex;
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private static Thread updateThread = null;
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private static PlayMessage[] pendingAudio = new PlayMessage[MAX_PENDING];
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public static boolean isServiceRunning() {
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return updateThread.isAlive();
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}
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/**
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* This method stops the Update Method's thread.
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*/
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public static void stopService() {
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if (updateThread != null) {
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updateThread.interrupt();
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}
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}
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/**
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* Starts the thread for the Update Method pattern if it was not started previously.
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* Also when the thread is is ready initializes the indexes of the queue
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*/
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public static void init() {
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if (updateThread == null) {
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updateThread = new Thread(new Runnable() {
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public void run() {
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while (!Thread.currentThread().isInterrupted()) {
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Audio.update();
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}
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}
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});
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}
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if (!updateThread.isAlive()) {
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updateThread.start();
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headIndex = 0;
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tailIndex = 0;
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}
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}
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/**
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* This method adds a new audio into the queue.
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* @param stream is the AudioInputStream for the method
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* @param volume is the level of the audio's volume
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*/
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public static void playSound(AudioInputStream stream, float volume) {
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init();
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// Walk the pending requests.
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for (int i = headIndex; i != tailIndex; i = (i + 1) % MAX_PENDING) {
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if (pendingAudio[i].stream == stream) {
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// Use the larger of the two volumes.
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pendingAudio[i].volume = Math.max(volume, pendingAudio[i].volume);
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// Don't need to enqueue.
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return;
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}
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}
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pendingAudio[tailIndex] = new PlayMessage();
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pendingAudio[tailIndex].stream = stream;
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pendingAudio[tailIndex].volume = volume;
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tailIndex = (tailIndex + 1) % MAX_PENDING;
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}
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/**
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* This method uses the Update Method pattern.
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* It takes the audio from the queue and plays it
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*/
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public static void update() {
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// If there are no pending requests, do nothing.
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if (headIndex == tailIndex) {
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return;
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}
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Clip clip = null;
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try {
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clip = AudioSystem.getClip();
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clip.open(pendingAudio[headIndex].stream);
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} catch (LineUnavailableException e) {
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System.err.println("Error occoured while loading the audio: The line is unavailable");
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e.printStackTrace();
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} catch (IOException e) {
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System.err.println("Input/Output error while loading the audio");
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e.printStackTrace();
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}
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clip.start();
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headIndex++;
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}
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}

‎event-queue/src/main/java/com/iluwatar/event/queue/PlayMessage.java‎

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

‎pom.xml‎

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<module>promise</module>
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<module>page-object</module>
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<module>event-asynchronous</module>
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<module>event-queue</module>
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<module>queue-load-leveling</module>
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<module>object-mother</module>
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<module>converter</module>

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