first commit

event-queue/pom.xml

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+<?xml version="1.0"?>
+<!--
+
+    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.
+
+-->
+<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"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>com.iluwatar</groupId>
+    <artifactId>java-design-patterns</artifactId>
+    <version>1.16.0-SNAPSHOT</version>
+  </parent>
+  <artifactId>event-queue</artifactId>
+  <dependencies>
+    <dependency>
+      <groupId>junit</groupId>
+      <artifactId>junit</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+</project>

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

@@ -0,0 +1,67 @@
+/**
+ * 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.BufferedReader;
+import java.io.File;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+import javax.sound.sampled.AudioInputStream;
+import javax.sound.sampled.AudioSystem;
+import javax.sound.sampled.UnsupportedAudioFileException;
+
+/**
+ * Event or message queues provide an asynchronous communications protocol, meaning that the sender
+ * and receiver of the message do not need to interact with the message queue at the same time. 
+ * Events or messages placed onto the queue are stored until the recipient retrieves them. Event 
+ * or message queues have implicit or explicit limits on the size of data that may be transmitted
+ * in a single message and the number of messages that may remain outstanding on the queue.
+ * A queue stores a series of notifications or requests in first-in, first-out order.
+ * Sending a notification enqueues the request and returns. The request processor then processes
+ * items from the queue at a later time.
+ */
+public class App {
+  /**
+   * Program entry point.
+   * 
+   * @param args command line args
+   * @throws IOException when there is a problem with the audio file loading
+   * @throws UnsupportedAudioFileException  when the loaded audio file is unsupported 
+   */
+  public static void main(String[] args) throws UnsupportedAudioFileException, IOException {
+    Audio.playSound(getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
+    Audio.playSound(getAudioStream("./etc/Closed-Hi-Hat-1.wav"), -8.0f);
+    
+    System.out.println("Press Enter key to stop the program...");
+    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    br.read();
+    Audio.stopService();
+  }
+  
+  public static AudioInputStream getAudioStream(String filePath) 
+      throws UnsupportedAudioFileException, IOException {
+    return AudioSystem.getAudioInputStream(new File(filePath).getAbsoluteFile());
+  }
+}

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

@@ -0,0 +1,131 @@
+/**
+ * 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++;
+  }
+}

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

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+/**
+ * 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 javax.sound.sampled.AudioInputStream;
+
+/**
+ * The Event Queue's queue will store the instances of this class.
+ * @author mkuprivecz
+ *
+ */
+public class PlayMessage {
+  AudioInputStream stream;
+  float volume;
+}

pom.xml

@@ -133,6 +133,7 @@
         <module>promise</module>
         <module>page-object</module>
         <module>event-asynchronous</module>
+		<module>event-queue</module>
         <module>queue-load-leveling</module>
         <module>object-mother</module>
         <module>converter</module>