Updated class diagram PNG

Fix redundant list alloc in LotteryNumbers

README.md

@@ -8,7 +8,6 @@
 [![License MIT](https://img.shields.io/badge/license-MIT-blue.svg)](https://raw.githubusercontent.com/iluwatar/java-design-patterns/master/LICENSE.md)
 [![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 [![Quality Gate](https://sonarcloud.io/api/project_badges/measure?project=com.iluwatar%3Ajava-design-patterns&metric=alert_status)](https://sonarcloud.io/dashboard/index/com.iluwatar%3Ajava-design-patterns)
-[![CII Best Practices](https://bestpractices.coreinfrastructure.org/projects/1503/badge)](https://bestpractices.coreinfrastructure.org/projects/1503)
 
 # Introduction
 

abstract-document/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>abstract-document</artifactId>
     <dependencies>

abstract-factory/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>abstract-factory</artifactId>
   <dependencies>

acyclic-visitor/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	
 	<artifactId>acyclic-visitor</artifactId>

adapter/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>adapter</artifactId>
   <dependencies>

aggregator-microservices/aggregator-service/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>aggregator-microservices</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

aggregator-microservices/information-microservice/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>aggregator-microservices</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

aggregator-microservices/inventory-microservice/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>aggregator-microservices</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

aggregator-microservices/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
     <artifactId>aggregator-microservices</artifactId>

ambassador/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>ambassador</artifactId>

api-gateway/api-gateway-service/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway-service</artifactId>

api-gateway/image-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
 
   <modelVersion>4.0.0</modelVersion>

api-gateway/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
   <artifactId>api-gateway</artifactId>

api-gateway/price-microservice/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>api-gateway</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
 
   <modelVersion>4.0.0</modelVersion>

async-method-invocation/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>async-method-invocation</artifactId>
   <dependencies>

balking/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

bridge/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>bridge</artifactId>
   <dependencies>

builder/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>builder</artifactId>
   <dependencies>

business-delegate/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>business-delegate</artifactId>
 	<dependencies>

caching/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>caching</artifactId>
   <dependencies>

callback/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>callback</artifactId>
   <dependencies>

chain/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>chain</artifactId>
   <dependencies>

collection-pipeline/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>collection-pipeline</artifactId>
   <dependencies>

command/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>command</artifactId>
   <dependencies>

composite/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>composite</artifactId>
   <dependencies>

converter/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
     <dependencies>

cqrs/pom.xml

@@ -21,7 +21,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>cqrs</artifactId>
 	<dependencies>

dao/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>dao</artifactId>
 

data-bus/pom.xml

@@ -33,7 +33,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>data-bus</artifactId>
     <dependencies>

data-mapper/pom.xml

@@ -28,7 +28,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>data-mapper</artifactId>
 	<dependencies>

data-transfer-object/pom.xml

@@ -28,7 +28,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>data-transfer-object</artifactId>
     <dependencies>

decorator/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>decorator</artifactId>
   <dependencies>

delegation/pom.xml

@@ -30,7 +30,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

dependency-injection/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>dependency-injection</artifactId>
   <dependencies>

dirty-flag/pom.xml

@@ -29,11 +29,11 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <groupId>com.iluwatar</groupId>
   <artifactId>dirty-flag</artifactId>
-  <version>1.20.0</version>
+  <version>1.21.0-SNAPSHOT</version>
   <name>dirty-flag</name>
   <url>http://maven.apache.org</url>
   <properties>

double-checked-locking/pom.xml

@@ -27,7 +27,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>double-checked-locking</artifactId>
   <dependencies>

double-dispatch/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>double-dispatch</artifactId>
   <dependencies>

eip-aggregator/pom.xml

@@ -26,7 +26,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
 
     <dependencies>

eip-message-channel/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>eip-message-channel</artifactId>
 	<dependencies>

eip-publish-subscribe/pom.xml

@@ -28,7 +28,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>eip-publish-subscribe</artifactId>
 	<dependencies>

eip-splitter/pom.xml

@@ -26,7 +26,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
 
     <dependencies>

eip-wire-tap/pom.xml

@@ -26,7 +26,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
 
     <dependencies>

event-aggregator/pom.xml

@@ -28,7 +28,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>event-aggregator</artifactId>
 	<dependencies>

event-asynchronous/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>event-asynchronous</artifactId>
   <dependencies>

event-driven-architecture/pom.xml

@@ -31,7 +31,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
 
     <artifactId>event-driven-architecture</artifactId>

event-queue/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>event-queue</artifactId>
   <dependencies>

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

@@ -47,13 +47,15 @@ public class App {
    * @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 {
+  public static void main(String[] args) throws UnsupportedAudioFileException, IOException, InterruptedException {
-    Audio.playSound(Audio.getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
+    Audio audio = Audio.getInstance();
-    Audio.playSound(Audio.getAudioStream("./etc/Closed-Hi-Hat-1.wav"), -8.0f);
+    audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
+    audio.playSound(audio.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));
+    try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
       br.read();
-    Audio.stopService();
+    }
+    audio.stopService();
   }
 }

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

@@ -23,6 +23,9 @@
 
 package com.iluwatar.event.queue;
 
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
 import java.io.File;
 import java.io.IOException;
 
@@ -38,49 +41,56 @@ import javax.sound.sampled.UnsupportedAudioFileException;
  *
  */
 public class Audio {
+  private static final Logger LOGGER = LoggerFactory.getLogger(Audio.class);
+  private static final Audio INSTANCE = new Audio();
 
   private static final int MAX_PENDING = 16;
 
-  private static int headIndex;
+  private int headIndex;
 
-  private static int tailIndex;
+  private int tailIndex;
 
-  private static Thread updateThread = null;
+  private volatile Thread updateThread = null;
 
-  private static PlayMessage[] pendingAudio = new PlayMessage[MAX_PENDING];
+  private PlayMessage[] pendingAudio = new PlayMessage[MAX_PENDING];
+
+  // Visible only for testing purposes
+  Audio() {
+
+  }
+
+  public static Audio getInstance() {
+    return INSTANCE;
+  }
 
   /**
-   * This method stops the Update Method's thread. 
+   * This method stops the Update Method's thread and waits till service stops.
    */
-  public static synchronized void stopService() {
+  public synchronized void stopService() throws InterruptedException {
     if (updateThread != null) {
       updateThread.interrupt();
     }
+    updateThread.join();
+    updateThread = null;
   }
   
   /**
    * This method check the Update Method's thread is started.
    * @return boolean
    */
-  public static synchronized boolean isServiceRunning() {
+  public synchronized boolean isServiceRunning() {
-    if (updateThread != null && updateThread.isAlive() ) {
+    return updateThread != null && updateThread.isAlive();
-      return true;
-    } else {
-      return false;
-    }
   }
 
   /**
    * 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() {
+  public void init() {
     if (updateThread == null) {
-      updateThread = new Thread(new Runnable() {
+      updateThread = new Thread(() -> {
-        public void run() {
         while (!Thread.currentThread().isInterrupted()) {
-            Audio.update();
+          update();
-          }
         }
       });
     }
@@ -90,7 +100,7 @@ public class Audio {
   /**
    * This is a synchronized thread starter
    */
-  public static synchronized void startThread() {
+  private synchronized void startThread() {
     if (!updateThread.isAlive()) {
       updateThread.start();
       headIndex = 0;
@@ -103,7 +113,7 @@ public class Audio {
    * @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) {
+  public void playSound(AudioInputStream stream, float volume) {
     init();
     // Walk the pending requests.
     for (int i = headIndex; i != tailIndex; i = (i + 1) % MAX_PENDING) {
@@ -123,7 +133,7 @@ public class Audio {
    * This method uses the Update Method pattern.
    * It takes the audio from the queue and plays it
    */
-  public static void update() {
+  private void update() {
     // If there are no pending requests, do nothing.
     if (headIndex == tailIndex) {
       return;
@@ -136,13 +146,11 @@ public class Audio {
       clip.open(audioStream);
       clip.start();
     } catch (LineUnavailableException e) {
-      System.err.println("Error occoured while loading the audio: The line is unavailable");
+      LOGGER.trace("Error occoured while loading the audio: The line is unavailable", e);
-      e.printStackTrace();
     } catch (IOException e) {
-      System.err.println("Input/Output error while loading the audio");
+      LOGGER.trace("Input/Output error while loading the audio", e);
-      e.printStackTrace();
     } catch (IllegalArgumentException e) {
-      System.err.println("The system doesn't support the sound: " + e.getMessage());
+      LOGGER.trace("The system doesn't support the sound: " + e.getMessage(), e);
     }
   }
 
@@ -153,7 +161,7 @@ public class Audio {
    * @throws UnsupportedAudioFileException when the audio file is not supported 
    * @throws IOException when the file is not readable
    */
-  public static AudioInputStream getAudioStream(String filePath) 
+  public AudioInputStream getAudioStream(String filePath)
       throws UnsupportedAudioFileException, IOException {
     return AudioSystem.getAudioInputStream(new File(filePath).getAbsoluteFile());
   }
@@ -162,7 +170,7 @@ public class Audio {
    * Returns with the message array of the queue 
    * @return PlayMessage[]
    */
-  public static PlayMessage[] getPendingAudio() {
+  public PlayMessage[] getPendingAudio() {
     return pendingAudio;
   }
 

event-queue/src/test/java/com/iluwatar/event/queue/AudioTest.java

@@ -23,6 +23,7 @@
 
 package com.iluwatar.event.queue;
 
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 import javax.sound.sampled.UnsupportedAudioFileException;
@@ -39,6 +40,12 @@ import static org.junit.jupiter.api.Assertions.assertTrue;
  */
 public class AudioTest {
 
+  private Audio audio;
+
+  @BeforeEach
+  void createAudioInstance() {
+    audio = new Audio();
+  }
   /**
    * Test here that the playSound method works correctly
    * @throws UnsupportedAudioFileException when the audio file is not supported 
@@ -47,13 +54,15 @@ public class AudioTest {
    */
   @Test
   public void testPlaySound() throws UnsupportedAudioFileException, IOException, InterruptedException {
-    Audio.playSound(Audio.getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
+    audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.wav"), -10.0f);
     // test that service is started
-    assertTrue(Audio.isServiceRunning());
+    assertTrue(audio.isServiceRunning());
     // adding a small pause to be sure that the sound is ended
     Thread.sleep(5000);
+
+    audio.stopService();
     // test that service is finished
-    assertFalse(!Audio.isServiceRunning());
+    assertFalse(audio.isServiceRunning());
   }
 
   /**
@@ -64,16 +73,18 @@ public class AudioTest {
    */
   @Test
   public void testQueue() throws UnsupportedAudioFileException, IOException, InterruptedException {
-    Audio.playSound(Audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
+    audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
-    Audio.playSound(Audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
+    audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
-    Audio.playSound(Audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
+    audio.playSound(audio.getAudioStream("./etc/Bass-Drum-1.aif"), -10.0f);
-    assertTrue(Audio.getPendingAudio().length > 0);
+    assertTrue(audio.getPendingAudio().length > 0);
     // test that service is started
-    assertTrue(Audio.isServiceRunning());
+    assertTrue(audio.isServiceRunning());
     // adding a small pause to be sure that the sound is ended
     Thread.sleep(10000);
+
+    audio.stopService();
     // test that service is finished
-    assertFalse(!Audio.isServiceRunning());
+    assertFalse(audio.isServiceRunning());
   }
 
 }

event-sourcing/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>event-sourcing</artifactId>
   <dependencies>

execute-around/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>execute-around</artifactId>
   <dependencies>

extension-objects/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

facade/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>facade</artifactId>
   <dependencies>

factory-kit/pom.xml

@@ -30,7 +30,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>factory-kit</artifactId>
     <dependencies>

factory-method/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>factory-method</artifactId>
   <dependencies>

feature-toggle/pom.xml

@@ -30,7 +30,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

fluentinterface/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

flux/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>flux</artifactId>
   <dependencies>

flyweight/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>flyweight</artifactId>
   <dependencies>

front-controller/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>front-controller</artifactId>
 	<dependencies>

guarded-suspension/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <packaging>jar</packaging>
   <artifactId>guarded-suspension</artifactId>

half-sync-half-async/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>half-sync-half-async</artifactId>
   <dependencies>

hexagonal/pom.xml

@@ -30,7 +30,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>hexagonal</artifactId>
   <dependencies>

hexagonal/src/main/java/com/iluwatar/hexagonal/domain/LotteryNumbers.java

@@ -22,13 +22,12 @@
  */
 package com.iluwatar.hexagonal.domain;
 
-import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
-import java.util.List;
 import java.util.PrimitiveIterator;
 import java.util.Random;
 import java.util.Set;
+import java.util.Iterator;
 
 /**
  *
@@ -85,11 +84,10 @@ public class LotteryNumbers {
    * @return numbers as comma separated string
    */
   public String getNumbersAsString() {
-    List<Integer> list = new ArrayList<>();
-    list.addAll(numbers);
     StringBuilder builder = new StringBuilder();
+    Iterator<Integer> iterator = numbers.iterator();
     for (int i = 0; i < NUM_NUMBERS; i++) {
-      builder.append(list.get(i));
+      builder.append(iterator.next());
       if (i < NUM_NUMBERS - 1) {
         builder.append(",");
       }

intercepting-filter/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>intercepting-filter</artifactId>
   <dependencies>

interpreter/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>interpreter</artifactId>
   <dependencies>

iterator/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>iterator</artifactId>
   <dependencies>

layers/pom.xml

@@ -30,7 +30,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<groupId>com.iluwatar.layers</groupId>
 	<artifactId>layers</artifactId>

lazy-loading/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>lazy-loading</artifactId>
   <dependencies>

marker/pom.xml

@@ -24,7 +24,7 @@
   <parent>
     <artifactId>java-design-patterns</artifactId>
     <groupId>com.iluwatar</groupId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <modelVersion>4.0.0</modelVersion>
 

mediator/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>mediator</artifactId>
   <dependencies>

memento/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>memento</artifactId>
   <dependencies>

model-view-controller/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>model-view-controller</artifactId>
   <dependencies>

model-view-presenter/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>model-view-presenter</artifactId>
   <name>model-view-presenter</name>

module/pom.xml

@@ -28,7 +28,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>module</artifactId>
 	<dependencies>

monad/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>monad</artifactId>
     <dependencies>

monostate/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>monostate</artifactId>
   <dependencies>

multiton/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>multiton</artifactId>
   <dependencies>

mute-idiom/pom.xml

@@ -21,7 +21,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>java-design-patterns</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 	<artifactId>mute-idiom</artifactId>
 	<dependencies>

mutex/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>mutex</artifactId>
   <dependencies>

naked-objects/dom/pom.xml

@@ -16,7 +16,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>naked-objects</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>naked-objects-dom</artifactId>

naked-objects/fixture/pom.xml

@@ -16,7 +16,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>naked-objects</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>naked-objects-fixture</artifactId>

naked-objects/integtests/pom.xml

@@ -16,7 +16,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>naked-objects</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>naked-objects-integtests</artifactId>

naked-objects/pom.xml

@@ -15,7 +15,7 @@
 	<parent>
 		<artifactId>java-design-patterns</artifactId>
 		<groupId>com.iluwatar</groupId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>naked-objects</artifactId>
@@ -350,17 +350,17 @@
 			<dependency>
 				<groupId>${project.groupId}</groupId>
 				<artifactId>naked-objects-dom</artifactId>
-				<version>1.20.0</version>
+				<version>1.21.0-SNAPSHOT</version>
 			</dependency>
 			<dependency>
 				<groupId>${project.groupId}</groupId>
 				<artifactId>naked-objects-fixture</artifactId>
-				<version>1.20.0</version>
+				<version>1.21.0-SNAPSHOT</version>
 			</dependency>
 			<dependency>
 				<groupId>${project.groupId}</groupId>
 				<artifactId>naked-objects-webapp</artifactId>
-				<version>1.20.0</version>
+				<version>1.21.0-SNAPSHOT</version>
 			</dependency>
 
 		</dependencies>

naked-objects/webapp/pom.xml

@@ -16,7 +16,7 @@
 	<parent>
 		<groupId>com.iluwatar</groupId>
 		<artifactId>naked-objects</artifactId>
-		<version>1.20.0</version>
+		<version>1.21.0-SNAPSHOT</version>
 	</parent>
 
 	<artifactId>naked-objects-webapp</artifactId>

null-object/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>null-object</artifactId>
   <dependencies>

object-mother/pom.xml

@@ -30,7 +30,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>object-mother</artifactId>
     <dependencies>

object-pool/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>object-pool</artifactId>
   <dependencies>

observer/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>observer</artifactId>
   <dependencies>

page-object/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <groupId>com.iluwatar</groupId>
         <artifactId>java-design-patterns</artifactId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <artifactId>page-object</artifactId>
     <dependencies>

partial-response/pom.xml

@@ -29,7 +29,7 @@
     <parent>
         <artifactId>java-design-patterns</artifactId>
         <groupId>com.iluwatar</groupId>
-        <version>1.20.0</version>
+        <version>1.21.0-SNAPSHOT</version>
     </parent>
     <modelVersion>4.0.0</modelVersion>
 

poison-pill/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>poison-pill</artifactId>
   <dependencies>

pom.xml

@@ -21,7 +21,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
     <packaging>pom</packaging>
     <inceptionYear>2014</inceptionYear>
     <properties>

private-class-data/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>private-class-data</artifactId>
   <dependencies>

producer-consumer/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>producer-consumer</artifactId>
   <dependencies>

promise/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>promise</artifactId>
   <dependencies>

property/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>property</artifactId>
   <dependencies>

prototype/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>prototype</artifactId>
   <dependencies>

proxy/pom.xml

@@ -29,7 +29,7 @@
   <parent>
     <groupId>com.iluwatar</groupId>
     <artifactId>java-design-patterns</artifactId>
-    <version>1.20.0</version>
+    <version>1.21.0-SNAPSHOT</version>
   </parent>
   <artifactId>proxy</artifactId>
   <dependencies>