Java 11 migrate remaining q-r (#1121)

* Moves queue-load-leveling to Java 11

* Moves reactor to Java 11

* Moves reader-writer-lock to Java 11

* Moves repository to Java 11

* Moves resource-acquisition-is-initialization to Java 11

* Moves retry to Java 11

* Moves role-object to Java 11

queue-load-leveling/src/main/java/com/iluwatar/queue/load/leveling/App.java

@@ -78,17 +78,17 @@ public class App {
 
     try {
       // Create a MessageQueue object.
-      MessageQueue msgQueue = new MessageQueue();
+      var msgQueue = new MessageQueue();
 
       LOGGER.info("Submitting TaskGenerators and ServiceExecutor threads.");
 
       // Create three TaskGenerator threads. Each of them will submit different number of jobs.
-      final Runnable taskRunnable1 = new TaskGenerator(msgQueue, 5);
+      final var taskRunnable1 = new TaskGenerator(msgQueue, 5);
-      final Runnable taskRunnable2 = new TaskGenerator(msgQueue, 1);
+      final var taskRunnable2 = new TaskGenerator(msgQueue, 1);
-      final Runnable taskRunnable3 = new TaskGenerator(msgQueue, 2);
+      final var taskRunnable3 = new TaskGenerator(msgQueue, 2);
 
       // Create e service which should process the submitted jobs.
-      final Runnable srvRunnable = new ServiceExecutor(msgQueue);
+      final var srvRunnable = new ServiceExecutor(msgQueue);
 
       // Create a ThreadPool of 2 threads and
       // submit all Runnable task for execution to executor..

queue-load-leveling/src/main/java/com/iluwatar/queue/load/leveling/MessageQueue.java

@@ -40,7 +40,7 @@ public class MessageQueue {
 
   // Default constructor when called creates Blocking Queue object. 
   public MessageQueue() {
-    this.blkQueue = new ArrayBlockingQueue<Message>(1024);
+    this.blkQueue = new ArrayBlockingQueue<>(1024);
   }
 
   /**
@@ -62,13 +62,11 @@ public class MessageQueue {
    * them. Retrieves and removes the head of this queue, or returns null if this queue is empty.
    */
   public Message retrieveMsg() {
-    Message retrievedMsg = null;
     try {
-      retrievedMsg = blkQueue.poll();
+      return blkQueue.poll();
     } catch (Exception e) {
       LOGGER.error(e.getMessage());
     }
-
+    return null;
-    return retrievedMsg;
   }
-}
+}

queue-load-leveling/src/main/java/com/iluwatar/queue/load/leveling/ServiceExecutor.java

@@ -46,7 +46,7 @@ public class ServiceExecutor implements Runnable {
   public void run() {
     try {
       while (!Thread.currentThread().isInterrupted()) {
-        Message msg = msgQueue.retrieveMsg();
+        var msg = msgQueue.retrieveMsg();
 
         if (null != msg) {
           LOGGER.info(msg.toString() + " is served.");

queue-load-leveling/src/main/java/com/iluwatar/queue/load/leveling/TaskGenerator.java

@@ -63,12 +63,11 @@ public class TaskGenerator implements Task, Runnable {
    * submission TaskGenerator thread will sleep for 1 second.
    */
   public void run() {
-
+    var count = this.msgCount;
-    int count = this.msgCount;
 
     try {
       while (count > 0) {
-        String statusMsg = "Message-" + count + " submitted by " + Thread.currentThread().getName();
+        var statusMsg = "Message-" + count + " submitted by " + Thread.currentThread().getName();
         this.submit(new Message(statusMsg));
 
         LOGGER.info(statusMsg);

queue-load-leveling/src/test/java/com/iluwatar/queue/load/leveling/AppTest.java

@@ -25,15 +25,12 @@ package com.iluwatar.queue.load.leveling;
 
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
-
 /**
  * Application Test
  */
 public class AppTest {
   @Test
-  public void test() throws IOException {
+  public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

queue-load-leveling/src/test/java/com/iluwatar/queue/load/leveling/MessageQueueTest.java

@@ -23,25 +23,23 @@
 
 package com.iluwatar.queue.load.leveling;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
- * 
  * Test case for submitting and retrieving messages from Blocking Queue.
- * 
  */
 public class MessageQueueTest {
 
   @Test
   public void messageQueueTest() {
-    
+
-    MessageQueue msgQueue = new MessageQueue();
+    var msgQueue = new MessageQueue();
-    
+
     // submit message
     msgQueue.submitMsg(new Message("MessageQueue Test"));
-    
+
     // retrieve message
     assertEquals("MessageQueue Test", msgQueue.retrieveMsg().getMsg());
   }

queue-load-leveling/src/test/java/com/iluwatar/queue/load/leveling/MessageTest.java

@@ -23,23 +23,21 @@
 
 package com.iluwatar.queue.load.leveling;
 
-import org.junit.jupiter.api.Test;
-
 import static org.junit.jupiter.api.Assertions.assertEquals;
 
+import org.junit.jupiter.api.Test;
+
 /**
- * 
  * Test case for creating and checking the Message.
- * 
  */
 public class MessageTest {
-  
+
   @Test
   public void messageTest() {
-    
+
     // Parameterized constructor test.
-    String testMsg = "Message Test";
+    var testMsg = "Message Test";
-    Message msg = new Message(testMsg);
+    var msg = new Message(testMsg);
     assertEquals(testMsg, msg.getMsg());
   }
 }

queue-load-leveling/src/test/java/com/iluwatar/queue/load/leveling/TaskGenSrvExeTest.java

@@ -26,25 +26,23 @@ package com.iluwatar.queue.load.leveling;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
+ * Test case for submitting Message to Blocking Queue by TaskGenerator and retrieve the message by
- * Test case for submitting Message to Blocking Queue by TaskGenerator
+ * ServiceExecutor.
- * and retrieve the message by ServiceExecutor.
- * 
  */
 public class TaskGenSrvExeTest {
 
   @Test
   public void taskGeneratorTest() {
-    MessageQueue msgQueue = new MessageQueue();
+    var msgQueue = new MessageQueue();
-    
+
     // Create a task generator thread with 1 job to submit.
-    Runnable taskRunnable = new TaskGenerator(msgQueue, 1);
+    var taskRunnable = new TaskGenerator(msgQueue, 1);
-    Thread taskGenThr = new Thread(taskRunnable);
+    var taskGenThr = new Thread(taskRunnable);
     taskGenThr.start();
-    
+
     // Create a service executor thread.
-    Runnable srvRunnable = new ServiceExecutor(msgQueue);
+    var srvRunnable = new ServiceExecutor(msgQueue);
-    Thread srvExeThr = new Thread(srvRunnable);
+    var srvExeThr = new Thread(srvRunnable);
     srvExeThr.start();
   }
 

reactor/src/main/java/com/iluwatar/reactor/app/App.java

@@ -124,15 +124,17 @@ public class App {
      * This represents application specific business logic that dispatcher will call on appropriate
      * events. These events are read events in our example.
      */
-    LoggingHandler loggingHandler = new LoggingHandler();
+    var loggingHandler = new LoggingHandler();
 
     /*
      * Our application binds to multiple channels and uses same logging handler to handle incoming
      * log requests.
      */
-    reactor.registerChannel(tcpChannel(6666, loggingHandler))
+    reactor
+        .registerChannel(tcpChannel(6666, loggingHandler))
         .registerChannel(tcpChannel(6667, loggingHandler))
-        .registerChannel(udpChannel(6668, loggingHandler)).start();
+        .registerChannel(udpChannel(6668, loggingHandler))
+        .start();
   }
 
   /**
@@ -144,20 +146,20 @@ public class App {
   public void stop() throws InterruptedException, IOException {
     reactor.stop();
     dispatcher.stop();
-    for (AbstractNioChannel channel : channels) {
+    for (var channel : channels) {
       channel.getJavaChannel().close();
     }
   }
 
   private AbstractNioChannel tcpChannel(int port, ChannelHandler handler) throws IOException {
-    NioServerSocketChannel channel = new NioServerSocketChannel(port, handler);
+    var channel = new NioServerSocketChannel(port, handler);
     channel.bind();
     channels.add(channel);
     return channel;
   }
 
   private AbstractNioChannel udpChannel(int port, ChannelHandler handler) throws IOException {
-    NioDatagramChannel channel = new NioDatagramChannel(port, handler);
+    var channel = new NioDatagramChannel(port, handler);
     channel.bind();
     channels.add(channel);
     return channel;

reactor/src/main/java/com/iluwatar/reactor/app/AppClient.java

@@ -25,7 +25,6 @@ package com.iluwatar.reactor.app;
 
 import java.io.IOException;
 import java.io.InputStream;
-import java.io.OutputStream;
 import java.io.PrintWriter;
 import java.net.DatagramPacket;
 import java.net.DatagramSocket;
@@ -55,7 +54,7 @@ public class AppClient {
    * @throws IOException if any I/O error occurs.
    */
   public static void main(String[] args) throws IOException {
-    AppClient appClient = new AppClient();
+    var appClient = new AppClient();
     appClient.start();
   }
 
@@ -118,8 +117,8 @@ public class AppClient {
     @Override
     public void run() {
       try (Socket socket = new Socket(InetAddress.getLocalHost(), serverPort)) {
-        OutputStream outputStream = socket.getOutputStream();
+        var outputStream = socket.getOutputStream();
-        PrintWriter writer = new PrintWriter(outputStream);
+        var writer = new PrintWriter(outputStream);
         sendLogRequests(writer, socket.getInputStream());
       } catch (IOException e) {
         LOGGER.error("error sending requests", e);
@@ -128,12 +127,12 @@ public class AppClient {
     }
 
     private void sendLogRequests(PrintWriter writer, InputStream inputStream) throws IOException {
-      for (int i = 0; i < 4; i++) {
+      for (var i = 0; i < 4; i++) {
         writer.println(clientName + " - Log request: " + i);
         writer.flush();
 
-        byte[] data = new byte[1024];
+        var data = new byte[1024];
-        int read = inputStream.read(data, 0, data.length);
+        var read = inputStream.read(data, 0, data.length);
         if (read == 0) {
           LOGGER.info("Read zero bytes");
         } else {
@@ -167,17 +166,17 @@ public class AppClient {
 
     @Override
     public void run() {
-      try (DatagramSocket socket = new DatagramSocket()) {
+      try (var socket = new DatagramSocket()) {
-        for (int i = 0; i < 4; i++) {
+        for (var i = 0; i < 4; i++) {
 
-          String message = clientName + " - Log request: " + i;
+          var message = clientName + " - Log request: " + i;
-          DatagramPacket request =
+          var bytes = message.getBytes();
-              new DatagramPacket(message.getBytes(), message.getBytes().length, remoteAddress);
+          var request = new DatagramPacket(bytes, bytes.length, remoteAddress);
 
           socket.send(request);
 
-          byte[] data = new byte[1024];
+          var data = new byte[1024];
-          DatagramPacket reply = new DatagramPacket(data, data.length);
+          var reply = new DatagramPacket(data, data.length);
           socket.receive(reply);
           if (reply.getLength() == 0) {
             LOGGER.info("Read zero bytes");

reactor/src/main/java/com/iluwatar/reactor/app/LoggingHandler.java

@@ -54,7 +54,7 @@ public class LoggingHandler implements ChannelHandler {
       doLogging((ByteBuffer) readObject);
       sendReply(channel, key);
     } else if (readObject instanceof DatagramPacket) {
-      DatagramPacket datagram = (DatagramPacket) readObject;
+      var datagram = (DatagramPacket) readObject;
       doLogging(datagram.getData());
       sendReply(channel, datagram, key);
     } else {
@@ -71,14 +71,14 @@ public class LoggingHandler implements ChannelHandler {
      * Create a reply acknowledgement datagram packet setting the receiver to the sender of incoming
      * message.
      */
-    DatagramPacket replyPacket = new DatagramPacket(ByteBuffer.wrap(ACK));
+    var replyPacket = new DatagramPacket(ByteBuffer.wrap(ACK));
     replyPacket.setReceiver(incomingPacket.getSender());
 
     channel.write(replyPacket, key);
   }
 
   private static void sendReply(AbstractNioChannel channel, SelectionKey key) {
-    ByteBuffer buffer = ByteBuffer.wrap(ACK);
+    var buffer = ByteBuffer.wrap(ACK);
     channel.write(buffer, key);
   }
 

reactor/src/main/java/com/iluwatar/reactor/framework/AbstractNioChannel.java

@@ -46,8 +46,7 @@ public abstract class AbstractNioChannel {
 
   private final SelectableChannel channel;
   private final ChannelHandler handler;
-  private final Map<SelectableChannel, Queue<Object>> channelToPendingWrites =
+  private final Map<SelectableChannel, Queue<Object>> channelToPendingWrites;
-      new ConcurrentHashMap<>();
   private NioReactor reactor;
 
   /**
@@ -59,6 +58,7 @@ public abstract class AbstractNioChannel {
   public AbstractNioChannel(ChannelHandler handler, SelectableChannel channel) {
     this.handler = handler;
     this.channel = channel;
+    this.channelToPendingWrites = new ConcurrentHashMap<>();
   }
 
   /**
@@ -117,18 +117,14 @@ public abstract class AbstractNioChannel {
    * whole pending block of data at once.
    */
   void flush(SelectionKey key) throws IOException {
-    Queue<Object> pendingWrites = channelToPendingWrites.get(key.channel());
+    var pendingWrites = channelToPendingWrites.get(key.channel());
-    while (true) {
+    Object pendingWrite;
-      Object pendingWrite = pendingWrites.poll();
+    while ((pendingWrite = pendingWrites.poll()) != null) {
-      if (pendingWrite == null) {
-        // We don't have anything more to write so channel is interested in reading more data
-        reactor.changeOps(key, SelectionKey.OP_READ);
-        break;
-      }
-
       // ask the concrete channel to make sense of data and write it to java channel
       doWrite(pendingWrite, key);
     }
+    // We don't have anything more to write so channel is interested in reading more data
+    reactor.changeOps(key, SelectionKey.OP_READ);
   }
 
   /**
@@ -162,7 +158,7 @@ public abstract class AbstractNioChannel {
    * @param key  the key which is writable.
    */
   public void write(Object data, SelectionKey key) {
-    Queue<Object> pendingWrites = this.channelToPendingWrites.get(key.channel());
+    var pendingWrites = this.channelToPendingWrites.get(key.channel());
     if (pendingWrites == null) {
       synchronized (this.channelToPendingWrites) {
         pendingWrites = this.channelToPendingWrites.get(key.channel());

reactor/src/main/java/com/iluwatar/reactor/framework/NioDatagramChannel.java

@@ -73,15 +73,15 @@ public class NioDatagramChannel extends AbstractNioChannel {
    */
   @Override
   public DatagramPacket read(SelectionKey key) throws IOException {
-    ByteBuffer buffer = ByteBuffer.allocate(1024);
+    var buffer = ByteBuffer.allocate(1024);
-    SocketAddress sender = ((DatagramChannel) key.channel()).receive(buffer);
+    var sender = ((DatagramChannel) key.channel()).receive(buffer);
 
     /*
      * It is required to create a DatagramPacket because we need to preserve which socket address
      * acts as destination for sending reply packets.
      */
     buffer.flip();
-    DatagramPacket packet = new DatagramPacket(buffer);
+    var packet = new DatagramPacket(buffer);
     packet.setSender(sender);
 
     return packet;
@@ -115,7 +115,7 @@ public class NioDatagramChannel extends AbstractNioChannel {
    */
   @Override
   protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException {
-    DatagramPacket pendingPacket = (DatagramPacket) pendingWrite;
+    var pendingPacket = (DatagramPacket) pendingWrite;
     getJavaChannel().send(pendingPacket.getData(), pendingPacket.getReceiver());
   }
 

reactor/src/main/java/com/iluwatar/reactor/framework/NioReactor.java

@@ -27,10 +27,7 @@ import java.io.IOException;
 import java.nio.channels.SelectionKey;
 import java.nio.channels.Selector;
 import java.nio.channels.ServerSocketChannel;
-import java.nio.channels.SocketChannel;
-import java.util.Iterator;
 import java.util.Queue;
-import java.util.Set;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
@@ -119,20 +116,15 @@ public class NioReactor {
    * @throws IOException if any I/O error occurs.
    */
   public NioReactor registerChannel(AbstractNioChannel channel) throws IOException {
-    SelectionKey key = channel.getJavaChannel().register(selector, channel.getInterestedOps());
+    var key = channel.getJavaChannel().register(selector, channel.getInterestedOps());
     key.attach(channel);
     channel.setReactor(this);
     return this;
   }
 
   private void eventLoop() throws IOException {
-    while (true) {
+    // honor interrupt request
-
+    while (!Thread.interrupted()) {
-      // honor interrupt request
-      if (Thread.interrupted()) {
-        break;
-      }
-
       // honor any pending commands first
       processPendingCommands();
 
@@ -145,12 +137,11 @@ public class NioReactor {
       /*
        * Represents the events that have occurred on registered handles.
        */
-      Set<SelectionKey> keys = selector.selectedKeys();
+      var keys = selector.selectedKeys();
-
+      var iterator = keys.iterator();
-      Iterator<SelectionKey> iterator = keys.iterator();
 
       while (iterator.hasNext()) {
-        SelectionKey key = iterator.next();
+        var key = iterator.next();
         if (!key.isValid()) {
           iterator.remove();
           continue;
@@ -162,9 +153,9 @@ public class NioReactor {
   }
 
   private void processPendingCommands() {
-    Iterator<Runnable> iterator = pendingCommands.iterator();
+    var iterator = pendingCommands.iterator();
     while (iterator.hasNext()) {
-      Runnable command = iterator.next();
+      var command = iterator.next();
       command.run();
       iterator.remove();
     }
@@ -185,15 +176,14 @@ public class NioReactor {
   }
 
   private static void onChannelWritable(SelectionKey key) throws IOException {
-    AbstractNioChannel channel = (AbstractNioChannel) key.attachment();
+    var channel = (AbstractNioChannel) key.attachment();
     channel.flush(key);
   }
 
   private void onChannelReadable(SelectionKey key) {
     try {
       // reads the incoming data in context of reactor main loop. Can this be improved?
-      Object readObject = ((AbstractNioChannel) key.attachment()).read(key);
+      var readObject = ((AbstractNioChannel) key.attachment()).read(key);
-
       dispatchReadEvent(key, readObject);
     } catch (IOException e) {
       try {
@@ -212,10 +202,10 @@ public class NioReactor {
   }
 
   private void onChannelAcceptable(SelectionKey key) throws IOException {
-    ServerSocketChannel serverSocketChannel = (ServerSocketChannel) key.channel();
+    var serverSocketChannel = (ServerSocketChannel) key.channel();
-    SocketChannel socketChannel = serverSocketChannel.accept();
+    var socketChannel = serverSocketChannel.accept();
     socketChannel.configureBlocking(false);
-    SelectionKey readKey = socketChannel.register(selector, SelectionKey.OP_READ);
+    var readKey = socketChannel.register(selector, SelectionKey.OP_READ);
     readKey.attach(key.attachment());
   }
 

reactor/src/main/java/com/iluwatar/reactor/framework/NioServerSocketChannel.java

@@ -83,9 +83,9 @@ public class NioServerSocketChannel extends AbstractNioChannel {
    */
   @Override
   public ByteBuffer read(SelectionKey key) throws IOException {
-    SocketChannel socketChannel = (SocketChannel) key.channel();
+    var socketChannel = (SocketChannel) key.channel();
-    ByteBuffer buffer = ByteBuffer.allocate(1024);
+    var buffer = ByteBuffer.allocate(1024);
-    int read = socketChannel.read(buffer);
+    var read = socketChannel.read(buffer);
     buffer.flip();
     if (read == -1) {
       throw new IOException("Socket closed");
@@ -100,9 +100,9 @@ public class NioServerSocketChannel extends AbstractNioChannel {
    */
   @Override
   public void bind() throws IOException {
-    getJavaChannel().socket().bind(
+    var javaChannel = getJavaChannel();
-        new InetSocketAddress(InetAddress.getLocalHost(), port));
+    javaChannel.socket().bind(new InetSocketAddress(InetAddress.getLocalHost(), port));
-    getJavaChannel().configureBlocking(false);
+    javaChannel.configureBlocking(false);
     LOGGER.info("Bound TCP socket at port: {}", port);
   }
 
@@ -112,7 +112,7 @@ public class NioServerSocketChannel extends AbstractNioChannel {
    */
   @Override
   protected void doWrite(Object pendingWrite, SelectionKey key) throws IOException {
-    ByteBuffer pendingBuffer = (ByteBuffer) pendingWrite;
+    var pendingBuffer = (ByteBuffer) pendingWrite;
     ((SocketChannel) key.channel()).write(pendingBuffer);
   }
 }

reactor/src/test/java/com/iluwatar/reactor/app/ReactorTest.java

@@ -25,14 +25,12 @@ package com.iluwatar.reactor.app;
 
 import com.iluwatar.reactor.framework.SameThreadDispatcher;
 import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
+import java.io.IOException;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.IOException;
-
 /**
- * 
  * This class tests the Distributed Logging service by starting a Reactor and then sending it
  * concurrent logging requests using multiple clients.
  */
@@ -42,17 +40,17 @@ public class ReactorTest {
 
   /**
    * Test the application using pooled thread dispatcher.
-   * 
+   *
-   * @throws IOException if any I/O error occurs.
+   * @throws IOException          if any I/O error occurs.
    * @throws InterruptedException if interrupted while stopping the application.
    */
   @Test
   public void testAppUsingThreadPoolDispatcher() throws IOException, InterruptedException {
     LOGGER.info("testAppUsingThreadPoolDispatcher start");
-    App app = new App(new ThreadPoolDispatcher(2));
+    var app = new App(new ThreadPoolDispatcher(2));
     app.start();
 
-    AppClient client = new AppClient();
+    var client = new AppClient();
     client.start();
 
     // allow clients to send requests. Artificial delay.
@@ -70,17 +68,17 @@ public class ReactorTest {
 
   /**
    * Test the application using same thread dispatcher.
-   * 
+   *
-   * @throws IOException if any I/O error occurs.
+   * @throws IOException          if any I/O error occurs.
    * @throws InterruptedException if interrupted while stopping the application.
    */
   @Test
   public void testAppUsingSameThreadDispatcher() throws IOException, InterruptedException {
     LOGGER.info("testAppUsingSameThreadDispatcher start");
-    App app = new App(new SameThreadDispatcher());
+    var app = new App(new SameThreadDispatcher());
     app.start();
 
-    AppClient client = new AppClient();
+    var client = new AppClient();
     client.start();
 
     // allow clients to send requests. Artificial delay.

reader-writer-lock/src/main/java/com/iluwatar/reader/writer/lock/App.java

@@ -23,11 +23,9 @@
 
 package com.iluwatar.reader.writer.lock;
 
-import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ThreadLocalRandom;
 import java.util.concurrent.TimeUnit;
-import java.util.stream.IntStream;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -58,19 +56,21 @@ public class App {
    */
   public static void main(String[] args) {
 
-    ExecutorService executeService = Executors.newFixedThreadPool(10);
+    var executeService = Executors.newFixedThreadPool(10);
-    ReaderWriterLock lock = new ReaderWriterLock();
+    var lock = new ReaderWriterLock();
 
     // Start writers
-    IntStream.range(0, 5)
+    for (var i = 0; i < 5; i++) {
-        .forEach(i -> executeService.submit(new Writer("Writer " + i, lock.writeLock(),
+      var writingTime = ThreadLocalRandom.current().nextLong(5000);
-            ThreadLocalRandom.current().nextLong(5000))));
+      executeService.submit(new Writer("Writer " + i, lock.writeLock(), writingTime));
+    }
     LOGGER.info("Writers added...");
 
     // Start readers
-    IntStream.range(0, 5)
+    for (var i = 0; i < 5; i++) {
-        .forEach(i -> executeService.submit(new Reader("Reader " + i, lock.readLock(),
+      var readingTime = ThreadLocalRandom.current().nextLong(10);
-            ThreadLocalRandom.current().nextLong(10))));
+      executeService.submit(new Reader("Reader " + i, lock.readLock(), readingTime));
+    }
     LOGGER.info("Readers added...");
 
     try {
@@ -81,9 +81,10 @@ public class App {
     }
 
     // Start readers
-    IntStream.range(6, 10)
+    for (var i = 6; i < 10; i++) {
-        .forEach(i -> executeService.submit(new Reader("Reader " + i, lock.readLock(),
+      var readingTime = ThreadLocalRandom.current().nextLong(10);
-            ThreadLocalRandom.current().nextLong(10))));
+      executeService.submit(new Reader("Reader " + i, lock.readLock(), readingTime));
+    }
     LOGGER.info("More readers added...");
 
 

reader-writer-lock/src/main/java/com/iluwatar/reader/writer/lock/ReaderWriterLock.java

@@ -43,7 +43,7 @@ public class ReaderWriterLock implements ReadWriteLock {
   private static final Logger LOGGER = LoggerFactory.getLogger(ReaderWriterLock.class);
 
 
-  private Object readerMutex = new Object();
+  private final Object readerMutex = new Object();
 
   private int currentReaderCount;
 
@@ -57,7 +57,7 @@ public class ReaderWriterLock implements ReadWriteLock {
    *
    * <p>This is the most important field in this class to control the access for reader/writer.
    */
-  private Set<Object> globalMutex = new HashSet<>();
+  private final Set<Object> globalMutex = new HashSet<>();
 
   private ReadLock readerLock = new ReadLock();
   private WriteLock writerLock = new WriteLock();
@@ -114,8 +114,8 @@ public class ReaderWriterLock implements ReadWriteLock {
           try {
             globalMutex.wait();
           } catch (InterruptedException e) {
-            LOGGER
+            var message = "InterruptedException while waiting for globalMutex in acquireForReaders";
-                .info("InterruptedException while waiting for globalMutex in acquireForReaders", e);
+            LOGGER.info(message, e);
             Thread.currentThread().interrupt();
           }
         }
@@ -125,7 +125,6 @@ public class ReaderWriterLock implements ReadWriteLock {
 
     @Override
     public void unlock() {
-
       synchronized (readerMutex) {
         currentReaderCount--;
         // Release the lock only when it is the last reader, it is ensure that the lock is released
@@ -142,7 +141,7 @@ public class ReaderWriterLock implements ReadWriteLock {
     }
 
     @Override
-    public void lockInterruptibly() throws InterruptedException {
+    public void lockInterruptibly() {
       throw new UnsupportedOperationException();
     }
 
@@ -152,7 +151,7 @@ public class ReaderWriterLock implements ReadWriteLock {
     }
 
     @Override
-    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
+    public boolean tryLock(long time, TimeUnit unit) {
       throw new UnsupportedOperationException();
     }
 
@@ -170,7 +169,6 @@ public class ReaderWriterLock implements ReadWriteLock {
 
     @Override
     public void lock() {
-
       synchronized (globalMutex) {
 
         // Wait until the lock is free.
@@ -189,7 +187,6 @@ public class ReaderWriterLock implements ReadWriteLock {
 
     @Override
     public void unlock() {
-
       synchronized (globalMutex) {
         globalMutex.remove(this);
         // Notify the waiter, other writer or reader
@@ -198,7 +195,7 @@ public class ReaderWriterLock implements ReadWriteLock {
     }
 
     @Override
-    public void lockInterruptibly() throws InterruptedException {
+    public void lockInterruptibly() {
       throw new UnsupportedOperationException();
     }
 
@@ -208,7 +205,7 @@ public class ReaderWriterLock implements ReadWriteLock {
     }
 
     @Override
-    public boolean tryLock(long time, TimeUnit unit) throws InterruptedException {
+    public boolean tryLock(long time, TimeUnit unit) {
       throw new UnsupportedOperationException();
     }
 

reader-writer-lock/src/test/java/com/iluwatar/reader/writer/lock/AppTest.java

@@ -31,9 +31,8 @@ import org.junit.jupiter.api.Test;
 public class AppTest {
 
   @Test
-  public void test() throws Exception {
+  public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
 
   }
 }

reader-writer-lock/src/test/java/com/iluwatar/reader/writer/lock/ReaderAndWriterTest.java

@@ -23,19 +23,17 @@
 
 package com.iluwatar.reader.writer.lock;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.iluwatar.reader.writer.lock.utils.InMemoryAppender;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 /**
  * @author hongshuwei@gmail.com
  */
@@ -61,12 +59,12 @@ public class ReaderAndWriterTest {
   @Test
   public void testReadAndWrite() throws Exception {
 
-    ReaderWriterLock lock = new ReaderWriterLock();
+    var lock = new ReaderWriterLock();
 
-    Reader reader1 = new Reader("Reader 1", lock.readLock());
+    var reader1 = new Reader("Reader 1", lock.readLock());
-    Writer writer1 = new Writer("Writer 1", lock.writeLock());
+    var writer1 = new Writer("Writer 1", lock.writeLock());
 
-    ExecutorService executeService = Executors.newFixedThreadPool(2);
+    var executeService = Executors.newFixedThreadPool(2);
     executeService.submit(reader1);
     // Let reader1 execute first
     Thread.sleep(150);
@@ -91,11 +89,11 @@ public class ReaderAndWriterTest {
   @Test
   public void testWriteAndRead() throws Exception {
 
-    ExecutorService executeService = Executors.newFixedThreadPool(2);
+    var executeService = Executors.newFixedThreadPool(2);
-    ReaderWriterLock lock = new ReaderWriterLock();
+    var lock = new ReaderWriterLock();
 
-    Reader reader1 = new Reader("Reader 1", lock.readLock());
+    var reader1 = new Reader("Reader 1", lock.readLock());
-    Writer writer1 = new Writer("Writer 1", lock.writeLock());
+    var writer1 = new Writer("Writer 1", lock.writeLock());
 
     executeService.submit(writer1);
     // Let writer1 execute first

reader-writer-lock/src/test/java/com/iluwatar/reader/writer/lock/ReaderTest.java

@@ -23,20 +23,18 @@
 
 package com.iluwatar.reader.writer.lock;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.spy;
+
 import com.iluwatar.reader.writer.lock.utils.InMemoryAppender;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.mockito.Mockito.spy;
-
 /**
  * @author hongshuwei@gmail.com
  */
@@ -62,11 +60,11 @@ public class ReaderTest {
   @Test
   public void testRead() throws Exception {
 
-    ExecutorService executeService = Executors.newFixedThreadPool(2);
+    var executeService = Executors.newFixedThreadPool(2);
-    ReaderWriterLock lock = new ReaderWriterLock();
+    var lock = new ReaderWriterLock();
 
-    Reader reader1 = spy(new Reader("Reader 1", lock.readLock()));
+    var reader1 = spy(new Reader("Reader 1", lock.readLock()));
-    Reader reader2 = spy(new Reader("Reader 2", lock.readLock()));
+    var reader2 = spy(new Reader("Reader 2", lock.readLock()));
 
     executeService.submit(reader1);
     Thread.sleep(150);

reader-writer-lock/src/test/java/com/iluwatar/reader/writer/lock/WriterTest.java

@@ -23,20 +23,18 @@
 
 package com.iluwatar.reader.writer.lock;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.spy;
+
 import com.iluwatar.reader.writer.lock.utils.InMemoryAppender;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
-import java.util.concurrent.TimeUnit;
-
-import static org.junit.jupiter.api.Assertions.assertTrue;
-import static org.mockito.Mockito.spy;
-
 /**
  * @author hongshuwei@gmail.com
  */
@@ -62,11 +60,11 @@ public class WriterTest {
   @Test
   public void testWrite() throws Exception {
 
-    ExecutorService executeService = Executors.newFixedThreadPool(2);
+    var executeService = Executors.newFixedThreadPool(2);
-    ReaderWriterLock lock = new ReaderWriterLock();
+    var lock = new ReaderWriterLock();
 
-    Writer writer1 = spy(new Writer("Writer 1", lock.writeLock()));
+    var writer1 = spy(new Writer("Writer 1", lock.writeLock()));
-    Writer writer2 = spy(new Writer("Writer 2", lock.writeLock()));
+    var writer2 = spy(new Writer("Writer 2", lock.writeLock()));
 
     executeService.submit(writer1);
     // Let write1 execute first

reader-writer-lock/src/test/java/com/iluwatar/reader/writer/lock/utils/InMemoryAppender.java

@@ -26,10 +26,9 @@ package com.iluwatar.reader.writer.lock.utils;
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
-import org.slf4j.LoggerFactory;
-
 import java.util.LinkedList;
 import java.util.List;
+import org.slf4j.LoggerFactory;
 
 /**
  * InMemory Log Appender Util.

repository/src/main/java/com/iluwatar/repository/App.java

@@ -24,7 +24,6 @@
 package com.iluwatar.repository;
 
 import java.util.List;
-import java.util.Optional;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
@@ -55,14 +54,13 @@ public class App {
    */
   public static void main(String[] args) {
 
-    ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
+    var context = new ClassPathXmlApplicationContext("applicationContext.xml");
-        "applicationContext.xml");
+    var repository = context.getBean(PersonRepository.class);
-    PersonRepository repository = context.getBean(PersonRepository.class);
 
-    Person peter = new Person("Peter", "Sagan", 17);
+    var peter = new Person("Peter", "Sagan", 17);
-    Person nasta = new Person("Nasta", "Kuzminova", 25);
+    var nasta = new Person("Nasta", "Kuzminova", 25);
-    Person john = new Person("John", "lawrence", 35);
+    var john = new Person("John", "lawrence", 35);
-    Person terry = new Person("Terry", "Law", 36);
+    var terry = new Person("Terry", "Law", 36);
 
     // Add new Person records
     repository.save(peter);
@@ -74,17 +72,15 @@ public class App {
     LOGGER.info("Count Person records: {}", repository.count());
 
     // Print all records
-    List<Person> persons = (List<Person>) repository.findAll();
+    var persons = (List<Person>) repository.findAll();
-    for (Person person : persons) {
+    persons.stream().map(Person::toString).forEach(LOGGER::info);
-      LOGGER.info(person.toString());
-    }
 
     // Update Person
     nasta.setName("Barbora");
     nasta.setSurname("Spotakova");
     repository.save(nasta);
 
-    LOGGER.info("Find by id 2: {}", repository.findById(2L).get());
+    repository.findById(2L).ifPresent(p -> LOGGER.info("Find by id 2: {}", p));
 
     // Remove record from Person
     repository.deleteById(2L);
@@ -93,16 +89,15 @@ public class App {
     LOGGER.info("Count Person records: {}", repository.count());
 
     // find by name
-    Optional<Person> p = repository.findOne(new PersonSpecifications.NameEqualSpec("John"));
+    repository
-    LOGGER.info("Find by John is {}", p.get());
+        .findOne(new PersonSpecifications.NameEqualSpec("John"))
+        .ifPresent(p -> LOGGER.info("Find by John is {}", p));
 
     // find by age
     persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
 
     LOGGER.info("Find Person with age between 20,40: ");
-    for (Person person : persons) {
+    persons.stream().map(Person::toString).forEach(LOGGER::info);
-      LOGGER.info(person.toString());
-    }
 
     repository.deleteAll();
 

repository/src/main/java/com/iluwatar/repository/AppConfig.java

@@ -25,7 +25,6 @@ package com.iluwatar.repository;
 
 import java.sql.SQLException;
 import java.util.List;
-import java.util.Optional;
 import java.util.Properties;
 import javax.sql.DataSource;
 import org.apache.commons.dbcp.BasicDataSource;
@@ -55,7 +54,7 @@ public class AppConfig {
    */
   @Bean(destroyMethod = "close")
   public DataSource dataSource() {
-    BasicDataSource basicDataSource = new BasicDataSource();
+    var basicDataSource = new BasicDataSource();
     basicDataSource.setDriverClassName("org.h2.Driver");
     basicDataSource.setUrl("jdbc:h2:~/databases/person");
     basicDataSource.setUsername("sa");
@@ -68,13 +67,11 @@ public class AppConfig {
    */
   @Bean
   public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
-    LocalContainerEntityManagerFactoryBean entityManager =
+    var entityManager = new LocalContainerEntityManagerFactoryBean();
-        new LocalContainerEntityManagerFactoryBean();
     entityManager.setDataSource(dataSource());
     entityManager.setPackagesToScan("com.iluwatar");
     entityManager.setPersistenceProvider(new HibernatePersistenceProvider());
     entityManager.setJpaProperties(jpaProperties());
-
     return entityManager;
   }
 
@@ -82,7 +79,7 @@ public class AppConfig {
    * Properties for Jpa.
    */
   private static Properties jpaProperties() {
-    Properties properties = new Properties();
+    var properties = new Properties();
     properties.setProperty("hibernate.dialect", "org.hibernate.dialect.H2Dialect");
     properties.setProperty("hibernate.hbm2ddl.auto", "create-drop");
     return properties;
@@ -93,7 +90,7 @@ public class AppConfig {
    */
   @Bean
   public JpaTransactionManager transactionManager() throws SQLException {
-    JpaTransactionManager transactionManager = new JpaTransactionManager();
+    var transactionManager = new JpaTransactionManager();
     transactionManager.setEntityManagerFactory(entityManagerFactory().getObject());
     return transactionManager;
   }
@@ -104,15 +101,13 @@ public class AppConfig {
    * @param args command line args
    */
   public static void main(String[] args) {
+    var context = new AnnotationConfigApplicationContext(AppConfig.class);
+    var repository = context.getBean(PersonRepository.class);
 
-    AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext(
+    var peter = new Person("Peter", "Sagan", 17);
-        AppConfig.class);
+    var nasta = new Person("Nasta", "Kuzminova", 25);
-    PersonRepository repository = context.getBean(PersonRepository.class);
+    var john = new Person("John", "lawrence", 35);
-
+    var terry = new Person("Terry", "Law", 36);
-    Person peter = new Person("Peter", "Sagan", 17);
-    Person nasta = new Person("Nasta", "Kuzminova", 25);
-    Person john = new Person("John", "lawrence", 35);
-    Person terry = new Person("Terry", "Law", 36);
 
     // Add new Person records
     repository.save(peter);
@@ -124,17 +119,15 @@ public class AppConfig {
     LOGGER.info("Count Person records: {}", repository.count());
 
     // Print all records
-    List<Person> persons = (List<Person>) repository.findAll();
+    var persons = (List<Person>) repository.findAll();
-    for (Person person : persons) {
+    persons.stream().map(Person::toString).forEach(LOGGER::info);
-      LOGGER.info(person.toString());
-    }
 
     // Update Person
     nasta.setName("Barbora");
     nasta.setSurname("Spotakova");
     repository.save(nasta);
 
-    LOGGER.info("Find by id 2: {}", repository.findById(2L).get());
+    repository.findById(2L).ifPresent(p -> LOGGER.info("Find by id 2: {}", p));
 
     // Remove record from Person
     repository.deleteById(2L);
@@ -143,16 +136,15 @@ public class AppConfig {
     LOGGER.info("Count Person records: {}", repository.count());
 
     // find by name
-    Optional<Person> p = repository.findOne(new PersonSpecifications.NameEqualSpec("John"));
+    repository
-    LOGGER.info("Find by John is {}", p.get());
+        .findOne(new PersonSpecifications.NameEqualSpec("John"))
+        .ifPresent(p -> LOGGER.info("Find by John is {}", p));
 
     // find by age
     persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
 
     LOGGER.info("Find Person with age between 20,40: ");
-    for (Person person : persons) {
+    persons.stream().map(Person::toString).forEach(LOGGER::info);
-      LOGGER.info(person.toString());
-    }
 
     context.close();
 

repository/src/main/java/com/iluwatar/repository/Person.java

@@ -92,9 +92,8 @@ public class Person {
 
   @Override
   public int hashCode() {
-
+    final var prime = 31;
-    final int prime = 31;
+    var result = 1;
-    int result = 1;
     result = prime * result + age;
     result = prime * result + (id == null ? 0 : id.hashCode());
     result = prime * result + (name == null ? 0 : name.hashCode());
@@ -113,7 +112,7 @@ public class Person {
     if (getClass() != obj.getClass()) {
       return false;
     }
-    Person other = (Person) obj;
+    var other = (Person) obj;
     if (age != other.age) {
       return false;
     }
@@ -132,13 +131,9 @@ public class Person {
       return false;
     }
     if (surname == null) {
-      if (other.surname != null) {
+      return other.surname == null;
-        return false;
-      }
-    } else if (!surname.equals(other.surname)) {
-      return false;
     }
-    return true;
+    return surname.equals(other.surname);
   }
 
 }

repository/src/main/java/com/iluwatar/repository/PersonSpecifications.java

@@ -50,9 +50,7 @@ public class PersonSpecifications {
 
     @Override
     public Predicate toPredicate(Root<Person> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
-
       return cb.between(root.get("age"), from, to);
-
     }
 
   }
@@ -72,9 +70,7 @@ public class PersonSpecifications {
      * Get predicate.
      */
     public Predicate toPredicate(Root<Person> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
-
       return cb.equal(root.get("name"), this.name);
-
     }
   }
 

repository/src/test/java/com/iluwatar/repository/AnnotationBasedRepositoryTest.java

@@ -23,7 +23,13 @@
 
 package com.iluwatar.repository;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.google.common.collect.Lists;
+import java.util.List;
+import javax.annotation.Resource;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -31,51 +37,41 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 
-import javax.annotation.Resource;
-import java.util.List;
-import java.util.Optional;
-
-import static org.junit.jupiter.api.Assertions.*;
-
 /**
  * Test case to test the functions of {@link PersonRepository}, beside the CRUD functions, the query
  * by {@link org.springframework.data.jpa.domain.Specification} are also test.
- * 
  */
 @ExtendWith(SpringExtension.class)
-@SpringBootTest(classes = { AppConfig.class })
+@SpringBootTest(classes = {AppConfig.class})
 public class AnnotationBasedRepositoryTest {
 
   @Resource
   private PersonRepository repository;
 
-  Person peter = new Person("Peter", "Sagan", 17);
+  private Person peter = new Person("Peter", "Sagan", 17);
-  Person nasta = new Person("Nasta", "Kuzminova", 25);
+  private Person nasta = new Person("Nasta", "Kuzminova", 25);
-  Person john = new Person("John", "lawrence", 35);
+  private Person john = new Person("John", "lawrence", 35);
-  Person terry = new Person("Terry", "Law", 36);
+  private Person terry = new Person("Terry", "Law", 36);
 
-  List<Person> persons = List.of(peter, nasta, john, terry);
+  private List<Person> persons = List.of(peter, nasta, john, terry);
 
   /**
    * Prepare data for test
    */
   @BeforeEach
   public void setup() {
-
     repository.saveAll(persons);
   }
 
   @Test
   public void testFindAll() {
-
+    var actuals = Lists.newArrayList(repository.findAll());
-    List<Person> actuals = Lists.newArrayList(repository.findAll());
     assertTrue(actuals.containsAll(persons) && persons.containsAll(actuals));
   }
 
   @Test
   public void testSave() {
-
+    var terry = repository.findByName("Terry");
-    Person terry = repository.findByName("Terry");
     terry.setSurname("Lee");
     terry.setAge(47);
     repository.save(terry);
@@ -87,8 +83,7 @@ public class AnnotationBasedRepositoryTest {
 
   @Test
   public void testDelete() {
-
+    var terry = repository.findByName("Terry");
-    Person terry = repository.findByName("Terry");
     repository.delete(terry);
 
     assertEquals(3, repository.count());
@@ -97,31 +92,26 @@ public class AnnotationBasedRepositoryTest {
 
   @Test
   public void testCount() {
-
     assertEquals(4, repository.count());
   }
 
   @Test
   public void testFindAllByAgeBetweenSpec() {
-
+    var persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
-    List<Person> persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
 
     assertEquals(3, persons.size());
-    assertTrue(persons.stream().allMatch((item) -> {
+    assertTrue(persons.stream().allMatch((item) -> item.getAge() > 20 && item.getAge() < 40));
-      return item.getAge() > 20 && item.getAge() < 40;
-    }));
   }
 
   @Test
   public void testFindOneByNameEqualSpec() {
-
+    var actual = repository.findOne(new PersonSpecifications.NameEqualSpec("Terry"));
-    Optional<Person> actual = repository.findOne(new PersonSpecifications.NameEqualSpec("Terry"));
+    assertTrue(actual.isPresent());
     assertEquals(terry, actual.get());
   }
 
   @AfterEach
   public void cleanup() {
-
     repository.deleteAll();
   }
 

repository/src/test/java/com/iluwatar/repository/AppConfigTest.java

@@ -23,6 +23,12 @@
 
 package com.iluwatar.repository;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+import java.sql.ResultSet;
+import java.sql.SQLException;
+import javax.sql.DataSource;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -30,19 +36,11 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 import org.springframework.transaction.annotation.Transactional;
 
-import javax.sql.DataSource;
-import java.sql.ResultSet;
-import java.sql.SQLException;
-
-import static org.junit.jupiter.api.Assertions.assertEquals;
-import static org.junit.jupiter.api.Assertions.assertNotNull;
-
 /**
  * This case is Just for test the Annotation Based configuration
- * 
  */
 @ExtendWith(SpringExtension.class)
-@SpringBootTest(classes = { AppConfig.class })
+@SpringBootTest(classes = {AppConfig.class})
 public class AppConfigTest {
 
   @Autowired
@@ -62,12 +60,11 @@ public class AppConfigTest {
   @Test
   @Transactional
   public void testQuery() throws SQLException {
-    ResultSet resultSet = dataSource.getConnection().createStatement().executeQuery("SELECT 1");
+    var resultSet = dataSource.getConnection().createStatement().executeQuery("SELECT 1");
+    var expected = "1";
     String result = null;
-    String expected = "1";
     while (resultSet.next()) {
       result = resultSet.getString(1);
-
     }
     assertEquals(expected, result);
   }

repository/src/test/java/com/iluwatar/repository/AppTest.java

@@ -25,15 +25,12 @@ package com.iluwatar.repository;
 
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
-
 /**
  * Tests that Repository example runs without errors.
  */
 public class AppTest {
   @Test
   public void test() {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

repository/src/test/java/com/iluwatar/repository/RepositoryTest.java

@@ -23,7 +23,13 @@
 
 package com.iluwatar.repository;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import com.google.common.collect.Lists;
+import java.util.List;
+import javax.annotation.Resource;
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
@@ -31,50 +37,41 @@ import org.junit.jupiter.api.extension.ExtendWith;
 import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.test.context.junit.jupiter.SpringExtension;
 
-import javax.annotation.Resource;
-import java.util.List;
-import java.util.Optional;
-
-import static org.junit.jupiter.api.Assertions.*;
-
 /**
  * Test case to test the functions of {@link PersonRepository}, beside the CRUD functions, the query
  * by {@link org.springframework.data.jpa.domain.Specification} are also test.
  */
 @ExtendWith(SpringExtension.class)
-@SpringBootTest(properties = { "locations=classpath:applicationContext.xml" })
+@SpringBootTest(properties = {"locations=classpath:applicationContext.xml"})
 public class RepositoryTest {
 
   @Resource
   private PersonRepository repository;
 
-  Person peter = new Person("Peter", "Sagan", 17);
+  private Person peter = new Person("Peter", "Sagan", 17);
-  Person nasta = new Person("Nasta", "Kuzminova", 25);
+  private Person nasta = new Person("Nasta", "Kuzminova", 25);
-  Person john = new Person("John", "lawrence", 35);
+  private Person john = new Person("John", "lawrence", 35);
-  Person terry = new Person("Terry", "Law", 36);
+  private Person terry = new Person("Terry", "Law", 36);
 
-  List<Person> persons = List.of(peter, nasta, john, terry);
+  private List<Person> persons = List.of(peter, nasta, john, terry);
 
   /**
    * Prepare data for test
    */
   @BeforeEach
   public void setup() {
-
     repository.saveAll(persons);
   }
 
   @Test
   public void testFindAll() {
-
+    var actuals = Lists.newArrayList(repository.findAll());
-    List<Person> actuals = Lists.newArrayList(repository.findAll());
     assertTrue(actuals.containsAll(persons) && persons.containsAll(actuals));
   }
 
   @Test
   public void testSave() {
-
+    var terry = repository.findByName("Terry");
-    Person terry = repository.findByName("Terry");
     terry.setSurname("Lee");
     terry.setAge(47);
     repository.save(terry);
@@ -86,8 +83,7 @@ public class RepositoryTest {
 
   @Test
   public void testDelete() {
-
+    var terry = repository.findByName("Terry");
-    Person terry = repository.findByName("Terry");
     repository.delete(terry);
 
     assertEquals(3, repository.count());
@@ -96,14 +92,12 @@ public class RepositoryTest {
 
   @Test
   public void testCount() {
-
     assertEquals(4, repository.count());
   }
 
   @Test
   public void testFindAllByAgeBetweenSpec() {
-
+    var persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
-    List<Person> persons = repository.findAll(new PersonSpecifications.AgeBetweenSpec(20, 40));
 
     assertEquals(3, persons.size());
     assertTrue(persons.stream().allMatch(item -> item.getAge() > 20 && item.getAge() < 40));
@@ -111,14 +105,13 @@ public class RepositoryTest {
 
   @Test
   public void testFindOneByNameEqualSpec() {
-
+    var actual = repository.findOne(new PersonSpecifications.NameEqualSpec("Terry"));
-    Optional<Person> actual = repository.findOne(new PersonSpecifications.NameEqualSpec("Terry"));
+    assertTrue(actual.isPresent());
     assertEquals(terry, actual.get());
   }
 
   @AfterEach
   public void cleanup() {
-
     repository.deleteAll();
   }
 

resource-acquisition-is-initialization/src/main/java/com/iluwatar/resource/acquisition/is/initialization/App.java

@@ -54,11 +54,11 @@ public class App {
    */
   public static void main(String[] args) throws Exception {
 
-    try (SlidingDoor slidingDoor = new SlidingDoor()) {
+    try (var ignored = new SlidingDoor()) {
       LOGGER.info("Walking in.");
     }
 
-    try (TreasureChest treasureChest = new TreasureChest()) {
+    try (var ignored = new TreasureChest()) {
       LOGGER.info("Looting contents.");
     }
   }

resource-acquisition-is-initialization/src/main/java/com/iluwatar/resource/acquisition/is/initialization/SlidingDoor.java

@@ -38,7 +38,7 @@ public class SlidingDoor implements AutoCloseable {
   }
 
   @Override
-  public void close() throws Exception {
+  public void close() {
     LOGGER.info("Sliding door closes.");
   }
 }

resource-acquisition-is-initialization/src/main/java/com/iluwatar/resource/acquisition/is/initialization/TreasureChest.java

@@ -24,7 +24,6 @@
 package com.iluwatar.resource.acquisition.is.initialization;
 
 import java.io.Closeable;
-import java.io.IOException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -40,7 +39,7 @@ public class TreasureChest implements Closeable {
   }
 
   @Override
-  public void close() throws IOException {
+  public void close() {
     LOGGER.info("Treasure chest closes.");
   }
 }

resource-acquisition-is-initialization/src/test/java/com/iluwatar/resource/acquisition/is/initialization/AppTest.java

@@ -26,15 +26,12 @@ package com.iluwatar.resource.acquisition.is.initialization;
 import org.junit.jupiter.api.Test;
 
 /**
- * 
  * Application test
- *
  */
 public class AppTest {
 
   @Test
   public void test() throws Exception {
-    String[] args = {};
+    App.main(new String[]{});
-    App.main(args);
   }
 }

resource-acquisition-is-initialization/src/test/java/com/iluwatar/resource/acquisition/is/initialization/ClosableTest.java

@@ -23,19 +23,18 @@
 
 package com.iluwatar.resource.acquisition.is.initialization;
 
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
 import ch.qos.logback.classic.Logger;
 import ch.qos.logback.classic.spi.ILoggingEvent;
 import ch.qos.logback.core.AppenderBase;
 import java.util.LinkedList;
 import java.util.List;
-
 import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.slf4j.LoggerFactory;
 
-import static org.junit.jupiter.api.Assertions.assertTrue;
-
 /**
  * Date: 12/28/15 - 9:31 PM
  *
@@ -56,8 +55,8 @@ public class ClosableTest {
   }
 
   @Test
-  public void testOpenClose() throws Exception {
+  public void testOpenClose() {
-    try (final SlidingDoor door = new SlidingDoor(); final TreasureChest chest = new TreasureChest()) {
+    try (final var ignored = new SlidingDoor(); final var ignored1 = new TreasureChest()) {
       assertTrue(appender.logContains("Sliding door opens."));
       assertTrue(appender.logContains("Treasure chest opens."));
     }

retry/README.md

@@ -78,7 +78,7 @@ to recover from this error.
 We can model a 'recoverable' scenario by instantiating `FindCustomer` like this:
 
 ```java
-final BusinessOperation<String> op = new FindCustomer(
+final var op = new FindCustomer(
     "12345",
     new CustomerNotFoundException("not found"),
     new CustomerNotFoundException("still not found"),
@@ -97,7 +97,7 @@ worker thread in the database subsystem typically needs 50ms to
 this:
 
 ```java
-final BusinessOperation<String> op = new Retry<>(
+final var op = new Retry<>(
     new FindCustomer(
         "1235",
         new CustomerNotFoundException("not found"),

retry/src/main/java/com/iluwatar/retry/App.java

@@ -90,14 +90,14 @@ public final class App {
   }
 
   private static void errorWithRetry() throws Exception {
-    final Retry<String> retry = new Retry<>(
+    final var retry = new Retry<>(
         new FindCustomer("123", new CustomerNotFoundException("not found")),
         3,  //3 attempts
         100, //100 ms delay between attempts
         e -> CustomerNotFoundException.class.isAssignableFrom(e.getClass())
     );
     op = retry;
-    final String customerId = op.perform();
+    final var customerId = op.perform();
     LOG.info(String.format(
         "However, retrying the operation while ignoring a recoverable error will eventually yield "
             + "the result %s after a number of attempts %s", customerId, retry.attempts()
@@ -105,14 +105,14 @@ public final class App {
   }
 
   private static void errorWithRetryExponentialBackoff() throws Exception {
-    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+    final var retry = new RetryExponentialBackoff<>(
         new FindCustomer("123", new CustomerNotFoundException("not found")),
         6,  //6 attempts
         30000, //30 s max delay between attempts
         e -> CustomerNotFoundException.class.isAssignableFrom(e.getClass())
     );
     op = retry;
-    final String customerId = op.perform();
+    final var customerId = op.perform();
     LOG.info(String.format(
         "However, retrying the operation while ignoring a recoverable error will eventually yield "
             + "the result %s after a number of attempts %s", customerId, retry.attempts()

retry/src/main/java/com/iluwatar/retry/RetryExponentialBackoff.java

@@ -100,8 +100,8 @@ public final class RetryExponentialBackoff<T> implements BusinessOperation<T> {
         }
 
         try {
-          long testDelay = (long) Math.pow(2, this.attempts()) * 1000 + RANDOM.nextInt(1000);
+          var testDelay = (long) Math.pow(2, this.attempts()) * 1000 + RANDOM.nextInt(1000);
-          long delay = testDelay < this.maxDelay ? testDelay : maxDelay;
+          var delay = Math.min(testDelay, this.maxDelay);
           Thread.sleep(delay);
         } catch (InterruptedException f) {
           //ignore

retry/src/test/java/com/iluwatar/retry/FindCustomerTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.retry;
 
-import org.junit.jupiter.api.Test;
-
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Unit tests for {@link FindCustomer}.
  *
@@ -40,33 +40,29 @@ public class FindCustomerTest {
    */
   @Test
   public void noExceptions() throws Exception {
-    assertThat(
+    assertThat(new FindCustomer("123").perform(), is("123"));
-        new FindCustomer("123").perform(),
-        is("123")
-    );
   }
 
   /**
    * Throws the given exception.
-   * 
+   *
    * @throws Exception the expected exception
    */
   @Test
   public void oneException() {
-    assertThrows(BusinessException.class, () -> {
+    var findCustomer = new FindCustomer("123", new BusinessException("test"));
-      new FindCustomer("123", new BusinessException("test")).perform();
+    assertThrows(BusinessException.class, findCustomer::perform);
-    });
   }
 
   /**
    * Should first throw the given exceptions, then return the given result.
-   * 
+   *
    * @throws Exception not an expected exception
    */
   @Test
   public void resultAfterExceptions() throws Exception {
-    final BusinessOperation<String> op = new FindCustomer(
+    final var op = new FindCustomer(
-        "123", 
+        "123",
         new CustomerNotFoundException("not found"),
         new DatabaseNotAvailableException("not available")
     );
@@ -81,9 +77,6 @@ public class FindCustomerTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(op.perform(), is("123"));
-        op.perform(),
-        is("123")
-    );
   }
 }

retry/src/test/java/com/iluwatar/retry/RetryExponentialBackoffTest.java

@@ -23,26 +23,27 @@
 
 package com.iluwatar.retry;
 
-import org.junit.jupiter.api.Test;
 import static org.hamcrest.CoreMatchers.hasItem;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Unit tests for {@link Retry}.
  *
  * @author George Aristy (george.aristy@gmail.com)
  */
 public class RetryExponentialBackoffTest {
-    /**
+  /**
-     * Should contain all errors thrown.
+   * Should contain all errors thrown.
-     */
+   */
   @Test
-  public void errors() throws Exception {
+  public void errors() {
-    final BusinessException e = new BusinessException("unhandled");
+    final var e = new BusinessException("unhandled");
-    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+    final var retry = new RetryExponentialBackoff<String>(
-        () -> { 
+        () -> {
-          throw e; 
+          throw e;
         },
         2,
         0
@@ -53,22 +54,19 @@ public class RetryExponentialBackoffTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.errors(), hasItem(e));
-        retry.errors(),
-        hasItem(e)
-    );
   }
 
-    /**
+  /**
-     * No exceptions will be ignored, hence final number of attempts should be 1 even if we're asking
+   * No exceptions will be ignored, hence final number of attempts should be 1 even if we're asking
-     * it to attempt twice.
+   * it to attempt twice.
-     */
+   */
   @Test
   public void attempts() {
-    final BusinessException e = new BusinessException("unhandled");
+    final var e = new BusinessException("unhandled");
-    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+    final var retry = new RetryExponentialBackoff<String>(
-        () -> { 
+        () -> {
-          throw e; 
+          throw e;
         },
         2,
         0
@@ -79,22 +77,19 @@ public class RetryExponentialBackoffTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.attempts(), is(1));
-        retry.attempts(),
-        is(1)
-    );
   }
 
-    /**
+  /**
-     * Final number of attempts should be equal to the number of attempts asked because we are
+   * Final number of attempts should be equal to the number of attempts asked because we are asking
-     * asking it to ignore the exception that will be thrown.
+   * it to ignore the exception that will be thrown.
-     */
+   */
   @Test
-  public void ignore() throws Exception {
+  public void ignore() {
-    final BusinessException e = new CustomerNotFoundException("customer not found");
+    final var e = new CustomerNotFoundException("customer not found");
-    final RetryExponentialBackoff<String> retry = new RetryExponentialBackoff<>(
+    final var retry = new RetryExponentialBackoff<String>(
-        () -> { 
+        () -> {
-          throw e; 
+          throw e;
         },
         2,
         0,
@@ -106,9 +101,6 @@ public class RetryExponentialBackoffTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.attempts(), is(2));
-        retry.attempts(),
-        is(2)
-    );
   }
 }

retry/src/test/java/com/iluwatar/retry/RetryTest.java

@@ -23,12 +23,12 @@
 
 package com.iluwatar.retry;
 
-import org.junit.jupiter.api.Test;
-
 import static org.hamcrest.CoreMatchers.hasItem;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.MatcherAssert.assertThat;
 
+import org.junit.jupiter.api.Test;
+
 /**
  * Unit tests for {@link Retry}.
  *
@@ -40,10 +40,11 @@ public class RetryTest {
    */
   @Test
   public void errors() {
-    final BusinessException e = new BusinessException("unhandled");
+    final var e = new BusinessException("unhandled");
-    final Retry<String> retry = new Retry<>(
+    final var retry = new Retry<String>(
         () -> {
-          throw e; },
+          throw e;
+        },
         2,
         0
     );
@@ -53,10 +54,7 @@ public class RetryTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.errors(), hasItem(e));
-        retry.errors(),
-        hasItem(e)
-    );
   }
 
   /**
@@ -65,10 +63,11 @@ public class RetryTest {
    */
   @Test
   public void attempts() {
-    final BusinessException e = new BusinessException("unhandled");
+    final var e = new BusinessException("unhandled");
-    final Retry<String> retry = new Retry<>(
+    final var retry = new Retry<String>(
         () -> {
-          throw e; },
+          throw e;
+        },
         2,
         0
     );
@@ -78,22 +77,20 @@ public class RetryTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.attempts(), is(1));
-        retry.attempts(),
-        is(1)
-    );
   }
 
   /**
-   * Final number of attempts should be equal to the number of attempts asked because we are 
+   * Final number of attempts should be equal to the number of attempts asked because we are asking
-   * asking it to ignore the exception that will be thrown.
+   * it to ignore the exception that will be thrown.
    */
   @Test
-  public void ignore() throws Exception {
+  public void ignore() {
-    final BusinessException e = new CustomerNotFoundException("customer not found");
+    final var e = new CustomerNotFoundException("customer not found");
-    final Retry<String> retry = new Retry<>(
+    final var retry = new Retry<String>(
         () -> {
-          throw e; },
+          throw e;
+        },
         2,
         0,
         ex -> CustomerNotFoundException.class.isAssignableFrom(ex.getClass())
@@ -104,10 +101,7 @@ public class RetryTest {
       //ignore
     }
 
-    assertThat(
+    assertThat(retry.attempts(), is(2));
-        retry.attempts(),
-        is(2)
-    );
   }
 
 }

role-object/src/main/java/com/iluwatar/roleobject/ApplicationRoleObject.java

@@ -30,37 +30,31 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * The Role Object pattern suggests to model context-specific views
+ * The Role Object pattern suggests to model context-specific views of an object as separate role
- * of an object as separate role objects which are
+ * objects which are dynamically attached to and removed from the core object. We call the resulting
- * dynamically attached to and removed from the core object.
+ * composite object structure, consisting of the core and its role objects, a subject. A subject
- * We call the resulting composite object structure,
+ * often plays several roles and the same role is likely to be played by different subjects. As an
- * consisting of the core and its role objects, a subject.
+ * example consider two different customers playing the role of borrower and investor, respectively.
- * A subject often plays several roles and the same role is likely to
+ * Both roles could as well be played by a single {@link Customer} object. The common superclass for
- * be played by different subjects.
+ * customer-specific roles is provided by {@link CustomerRole}, which also supports the {@link
- * As an example consider two different customers playing the role of borrower and
+ * Customer} interface.
- * investor, respectively. Both roles could as well be played by a single {@link Customer} object.
- * The common superclass for customer-specific roles is provided by {@link CustomerRole},
- * which also supports the {@link Customer} interface.
  *
  * <p>The {@link CustomerRole} class is abstract and not meant to be instantiated.
- * Concrete subclasses of {@link CustomerRole}, for example {@link BorrowerRole}
+ * Concrete subclasses of {@link CustomerRole}, for example {@link BorrowerRole} or {@link
- * or {@link InvestorRole}, define and implement the interface for specific roles. It is only
+ * InvestorRole}, define and implement the interface for specific roles. It is only these subclasses
- * these subclasses which are instantiated at runtime.
+ * which are instantiated at runtime. The {@link BorrowerRole}  class defines the context-specific
- * The {@link BorrowerRole}  class defines the context-specific view of {@link Customer}
+ * view of {@link Customer} objects as needed by the loan department. It defines additional
- * objects as needed by the loan department.
+ * operations to manage the customer’s credits and securities. Similarly, the {@link InvestorRole}
- * It defines additional operations to manage the customer’s
+ * class adds operations specific to the investment department’s view of customers. A client like
- * credits and securities. Similarly, the {@link InvestorRole} class adds operations specific
+ * the loan application may either work with objects of the {@link CustomerRole} class, using the
- * to the investment department’s view of customers.
+ * interface class {@link Customer}, or with objects of concrete {@link CustomerRole} subclasses.
- * A client like the loan application may either work with objects of the {@link CustomerRole}
+ * Suppose the loan application knows a particular {@link Customer} instance through its {@link
- * class, using the interface class {@link Customer}, or with objects of concrete
+ * Customer} interface. The loan application may want to check whether the {@link Customer} object
- * {@link CustomerRole} subclasses. Suppose the loan application knows a particular
+ * plays the role of Borrower. To this end it calls {@link Customer#hasRole(Role)} with a suitable
- * {@link Customer} instance through its {@link Customer} interface. The loan application
+ * role specification. For the purpose of our example, let’s assume we can name roles with enum. If
- * may want to check whether the {@link Customer} object plays the role of Borrower.
+ * the {@link Customer} object can play the role named “Borrower,” the loan application will ask it
- * To this end it calls {@link Customer#hasRole(Role)} with a suitable role specification. For
+ * to return a reference to the corresponding object. The loan application may now use this
- * the purpose of our example, let’s assume we can name roles with enum.
+ * reference to call Borrower-specific operations.
- * If the {@link Customer} object can play the role named “Borrower,” the loan application will
- * ask it to return a reference to the corresponding object.
- * The loan application may now use this reference to call Borrower-specific operations.
  */
 public class ApplicationRoleObject {
 
@@ -72,13 +66,13 @@ public class ApplicationRoleObject {
    * @param args program arguments
    */
   public static void main(String[] args) {
-    Customer customer = Customer.newCustomer(Borrower, Investor);
+    var customer = Customer.newCustomer(Borrower, Investor);
 
     logger.info(" the new customer created : {}", customer);
 
-    boolean hasBorrowerRole = customer.hasRole(Borrower);
+    var hasBorrowerRole = customer.hasRole(Borrower);
     logger.info(" customer has a borrowed role - {}", hasBorrowerRole);
-    boolean hasInvestorRole = customer.hasRole(Investor);
+    var hasInvestorRole = customer.hasRole(Investor);
     logger.info(" customer has an investor role - {}", hasInvestorRole);
 
     customer.getRole(Investor, InvestorRole.class)

role-object/src/main/java/com/iluwatar/roleobject/Customer.java

@@ -23,6 +23,7 @@
 
 package com.iluwatar.roleobject;
 
+import java.util.Arrays;
 import java.util.Optional;
 
 /**
@@ -32,6 +33,7 @@ public abstract class Customer {
 
   /**
    * Add specific role @see {@link Role}.
+   *
    * @param role to add
    * @return true if the operation has been successful otherwise false
    */
@@ -39,6 +41,7 @@ public abstract class Customer {
 
   /**
    * Check specific role @see {@link Role}.
+   *
    * @param role to check
    * @return true if the role exists otherwise false
    */
@@ -47,6 +50,7 @@ public abstract class Customer {
 
   /**
    * Remove specific role @see {@link Role}.
+   *
    * @param role to remove
    * @return true if the operation has been successful otherwise false
    */
@@ -54,6 +58,7 @@ public abstract class Customer {
 
   /**
    * Get specific instance associated with this role @see {@link Role}.
+   *
    * @param role         to get
    * @param expectedRole instance class expected to get
    * @return optional with value if the instance exists and corresponds expected class
@@ -67,14 +72,13 @@ public abstract class Customer {
 
   /**
    * Create {@link Customer} with given roles.
+   *
    * @param role roles
    * @return Customer
    */
   public static Customer newCustomer(Role... role) {
-    Customer customer = newCustomer();
+    var customer = newCustomer();
-    for (Role r : role) {
+    Arrays.stream(role).forEach(customer::addRole);
-      customer.addRole(r);
-    }
     return customer;
   }
 

role-object/src/main/java/com/iluwatar/roleobject/CustomerCore.java

@@ -73,7 +73,7 @@ public class CustomerCore extends Customer {
 
   @Override
   public String toString() {
-    String roles = Arrays.toString(this.roles.keySet().toArray());
+    var roles = Arrays.toString(this.roles.keySet().toArray());
     return "Customer{roles=" + roles + "}";
   }
 }

role-object/src/main/java/com/iluwatar/roleobject/CustomerRole.java

@@ -26,5 +26,5 @@ package com.iluwatar.roleobject;
 /**
  * Key abstraction for segregated roles.
  */
-public abstract class CustomerRole extends CustomerCore{
+public abstract class CustomerRole extends CustomerCore {
 }

role-object/src/main/java/com/iluwatar/roleobject/Role.java

@@ -24,7 +24,6 @@
 package com.iluwatar.roleobject;
 
 import java.util.Optional;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -48,7 +47,7 @@ public enum Role {
    */
   @SuppressWarnings("unchecked")
   public <T extends CustomerRole> Optional<T> instance() {
-    Class<? extends CustomerRole> typeCst = this.typeCst;
+    var typeCst = this.typeCst;
     try {
       return (Optional<T>) Optional.of(typeCst.newInstance());
     } catch (InstantiationException | IllegalAccessException e) {

role-object/src/test/java/com/iluwatar/roleobject/ApplicationRoleObjectTest.java

@@ -26,8 +26,8 @@ import org.junit.Test;
 
 public class ApplicationRoleObjectTest {
 
-    @Test
+  @Test
-    public void mainTest() {
+  public void mainTest() {
-        ApplicationRoleObject.main(new String[]{});
+    ApplicationRoleObject.main(new String[]{});
-    }
+  }
 }

role-object/src/test/java/com/iluwatar/roleobject/BorrowerRoleTest.java

@@ -25,16 +25,12 @@ package com.iluwatar.roleobject;
 import org.junit.Assert;
 import org.junit.Test;
 
-import static org.junit.Assert.*;
-
 public class BorrowerRoleTest {
 
-    @Test
+  @Test
-    public void borrowTest() {
+  public void borrowTest() {
-        BorrowerRole borrowerRole = new BorrowerRole();
+    var borrowerRole = new BorrowerRole();
-        borrowerRole.setName("test");
+    borrowerRole.setName("test");
-        String res = "Borrower test wants to get some money.";
+    Assert.assertEquals(borrowerRole.borrow(), "Borrower test wants to get some money.");
-
+  }
-        Assert.assertEquals(borrowerRole.borrow(),res);
-    }
 }

role-object/src/test/java/com/iluwatar/roleobject/CustomerCoreTest.java

@@ -22,82 +22,72 @@
  */
 package com.iluwatar.roleobject;
 
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
 import org.junit.Test;
 
-import java.util.Optional;
-
-import static org.junit.Assert.*;
-
 public class CustomerCoreTest {
 
-    @Test
+  @Test
-    public void addRole() {
+  public void addRole() {
-        CustomerCore core = new CustomerCore();
+    var core = new CustomerCore();
-        boolean add = core.addRole(Role.Borrower);
+    assertTrue(core.addRole(Role.Borrower));
-        assertTrue(add);
+  }
 
-    }
+  @Test
+  public void hasRole() {
+    var core = new CustomerCore();
+    core.addRole(Role.Borrower);
+    assertTrue(core.hasRole(Role.Borrower));
+    assertFalse(core.hasRole(Role.Investor));
+  }
 
-    @Test
+  @Test
-    public void hasRole() {
+  public void remRole() {
-        CustomerCore core = new CustomerCore();
+    var core = new CustomerCore();
-        core.addRole(Role.Borrower);
+    core.addRole(Role.Borrower);
 
-        boolean has = core.hasRole(Role.Borrower);
+    var bRole = core.getRole(Role.Borrower, BorrowerRole.class);
-        assertTrue(has);
+    assertTrue(bRole.isPresent());
 
-        boolean notHas = core.hasRole(Role.Investor);
+    assertTrue(core.remRole(Role.Borrower));
-        assertFalse(notHas);
-    }
 
-    @Test
+    var empt = core.getRole(Role.Borrower, BorrowerRole.class);
-    public void remRole() {
+    assertFalse(empt.isPresent());
-        CustomerCore core = new CustomerCore();
+  }
-        core.addRole(Role.Borrower);
 
-        Optional<BorrowerRole> bRole = core.getRole(Role.Borrower, BorrowerRole.class);
+  @Test
-        assertTrue(bRole.isPresent());
+  public void getRole() {
+    var core = new CustomerCore();
+    core.addRole(Role.Borrower);
 
-        boolean res = core.remRole(Role.Borrower);
+    var bRole = core.getRole(Role.Borrower, BorrowerRole.class);
-        assertTrue(res);
+    assertTrue(bRole.isPresent());
 
-        Optional<BorrowerRole> empt = core.getRole(Role.Borrower, BorrowerRole.class);
+    var nonRole = core.getRole(Role.Borrower, InvestorRole.class);
-        assertFalse(empt.isPresent());
+    assertFalse(nonRole.isPresent());
 
-    }
+    var invRole = core.getRole(Role.Investor, InvestorRole.class);
-
+    assertFalse(invRole.isPresent());
-    @Test
+  }
-    public void getRole() {
-        CustomerCore core = new CustomerCore();
-        core.addRole(Role.Borrower);
-
-        Optional<BorrowerRole> bRole = core.getRole(Role.Borrower, BorrowerRole.class);
-        assertTrue(bRole.isPresent());
-
-        Optional<InvestorRole> nonRole = core.getRole(Role.Borrower, InvestorRole.class);
-        assertFalse(nonRole.isPresent());
-
-        Optional<InvestorRole> invRole = core.getRole(Role.Investor, InvestorRole.class);
-        assertFalse(invRole.isPresent());
 
 
-    }
+  @Test
+  public void toStringTest() {
+    var core = new CustomerCore();
+    core.addRole(Role.Borrower);
+    assertEquals(core.toString(), "Customer{roles=[Borrower]}");
+
+    core = new CustomerCore();
+    core.addRole(Role.Investor);
+    assertEquals(core.toString(), "Customer{roles=[Investor]}");
+
+    core = new CustomerCore();
+    assertEquals(core.toString(), "Customer{roles=[]}");
 
 
-    @Test
+  }
-    public void toStringTest() {
-        CustomerCore core = new CustomerCore();
-        core.addRole(Role.Borrower);
-        assertEquals(core.toString(), "Customer{roles=[Borrower]}");
-
-        core = new CustomerCore();
-        core.addRole(Role.Investor);
-        assertEquals(core.toString(), "Customer{roles=[Investor]}");
-
-        core = new CustomerCore();
-        assertEquals(core.toString(), "Customer{roles=[]}");
-
-
-    }
 
 }

role-object/src/test/java/com/iluwatar/roleobject/InvestorRoleTest.java

@@ -27,12 +27,11 @@ import org.junit.Test;
 
 public class InvestorRoleTest {
 
-    @Test
+  @Test
-    public void investTest() {
+  public void investTest() {
-        InvestorRole investorRole = new InvestorRole();
+    var investorRole = new InvestorRole();
-        investorRole.setName("test");
+    investorRole.setName("test");
-        investorRole.setAmountToInvest(10);
+    investorRole.setAmountToInvest(10);
-        String res = "Investor test has invested 10 dollars";
+    Assert.assertEquals(investorRole.invest(), "Investor test has invested 10 dollars");
-        Assert.assertEquals(investorRole.invest(), res);
+  }
-    }
 }

role-object/src/test/java/com/iluwatar/roleobject/RoleTest.java

@@ -25,16 +25,12 @@ package com.iluwatar.roleobject;
 import org.junit.Assert;
 import org.junit.Test;
 
-import java.util.Optional;
-
-import static org.junit.Assert.*;
-
 public class RoleTest {
 
-    @Test
+  @Test
-    public void instanceTest() {
+  public void instanceTest() {
-        Optional<CustomerRole> instance = Role.Borrower.instance();
+    var instance = Role.Borrower.instance();
-        Assert.assertTrue(instance.isPresent());
+    Assert.assertTrue(instance.isPresent());
-        Assert.assertEquals(instance.get().getClass(),BorrowerRole.class);
+    Assert.assertEquals(instance.get().getClass(), BorrowerRole.class);
-    }
+  }
 }