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 static void main(String[] args) {
 
     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 Runnable taskRunnable2 = new TaskGenerator(msgQueue, 1);
-      final Runnable taskRunnable3 = new TaskGenerator(msgQueue, 2);
+      final var taskRunnable1 = new TaskGenerator(msgQueue, 5);
+      final var taskRunnable2 = new TaskGenerator(msgQueue, 1);
+      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 void submitMsg(Message msg) {
    * 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 retrievedMsg;
+    return null;
   }
-}
+}

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

@@ -46,7 +46,7 @@ public ServiceExecutor(MessageQueue msgQueue) {
   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 void submit(Message msg) {
    * submission TaskGenerator thread will sleep for 1 second.
    */
   public void run() {
-
-    int count = this.msgCount;
+    var 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 @@
 
 import org.junit.jupiter.api.Test;
 
-import java.io.IOException;
-
 /**
  * Application Test
  */
 public class AppTest {
   @Test
-  public void test() throws IOException {
-    String[] args = {};
-    App.main(args);
+  public void test() {
+    App.main(new String[]{});
   }
 }

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";
-    Message msg = new Message(testMsg);
+    var testMsg = "Message Test";
+    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 @@
 import org.junit.jupiter.api.Test;
 
 /**
- * 
- * Test case for submitting Message to Blocking Queue by TaskGenerator
- * and retrieve the message by ServiceExecutor.
- * 
+ * Test case for submitting Message to Blocking Queue by TaskGenerator 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);
-    Thread taskGenThr = new Thread(taskRunnable);
+    var taskRunnable = new TaskGenerator(msgQueue, 1);
+    var taskGenThr = new Thread(taskRunnable);
     taskGenThr.start();
-    
+
     // Create a service executor thread.
-    Runnable srvRunnable = new ServiceExecutor(msgQueue);
-    Thread srvExeThr = new Thread(srvRunnable);
+    var srvRunnable = new ServiceExecutor(msgQueue);
+    var srvExeThr = new Thread(srvRunnable);
     srvExeThr.start();
   }
 

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

@@ -124,15 +124,17 @@ public void start() throws IOException {
      * 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 void start() throws IOException {
   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 @@
 
 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 TcpLoggingClient(String clientName, int serverPort) {
     @Override
     public void run() {
       try (Socket socket = new Socket(InetAddress.getLocalHost(), serverPort)) {
-        OutputStream outputStream = socket.getOutputStream();
-        PrintWriter writer = new PrintWriter(outputStream);
+        var outputStream = socket.getOutputStream();
+        var writer = new PrintWriter(outputStream);
         sendLogRequests(writer, socket.getInputStream());
       } catch (IOException e) {
         LOGGER.error("error sending requests", e);
@@ -128,12 +127,12 @@ public void run() {
     }
 
     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];
-        int read = inputStream.read(data, 0, data.length);
+        var data = new byte[1024];
+        var read = inputStream.read(data, 0, data.length);
         if (read == 0) {
           LOGGER.info("Read zero bytes");
         } else {
@@ -167,17 +166,17 @@ public UdpLoggingClient(String clientName, int port) throws UnknownHostException
 
     @Override
     public void run() {
-      try (DatagramSocket socket = new DatagramSocket()) {
-        for (int i = 0; i < 4; i++) {
+      try (var socket = new DatagramSocket()) {
+        for (var i = 0; i < 4; i++) {
 
-          String message = clientName + " - Log request: " + i;
-          DatagramPacket request =
-              new DatagramPacket(message.getBytes(), message.getBytes().length, remoteAddress);
+          var message = clientName + " - Log request: " + i;
+          var bytes = message.getBytes();
+          var request = new DatagramPacket(bytes, bytes.length, remoteAddress);
 
           socket.send(request);
 
-          byte[] data = new byte[1024];
-          DatagramPacket reply = new DatagramPacket(data, data.length);
+          var data = new byte[1024];
+          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 void handleChannelRead(AbstractNioChannel channel, Object readObject, Sel
       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 @@ private static void sendReply(
      * 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 =
-      new ConcurrentHashMap<>();
+  private final Map<SelectableChannel, Queue<Object>> channelToPendingWrites;
   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 ChannelHandler getHandler() {
    * whole pending block of data at once.
    */
   void flush(SelectionKey key) throws IOException {
-    Queue<Object> pendingWrites = channelToPendingWrites.get(key.channel());
-    while (true) {
-      Object pendingWrite = pendingWrites.poll();
-      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;
-      }
-
+    var pendingWrites = channelToPendingWrites.get(key.channel());
+    Object pendingWrite;
+    while ((pendingWrite = pendingWrites.poll()) != null) {
       // 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 @@ void flush(SelectionKey key) throws IOException {
    * @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());