Resolves checkstyle errors for patterns starting with letter r (#1072)

* Reduces checkstyle errors in reactor

* Reduces checkstyle errors in reader-writer-lock

* Reduces checkstyle errors in repository

* Reduces checkstyle errors in resource-acquisition-is-initialization

* Reduces checkstyle errors in retry

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

@@ -23,10 +23,6 @@
 
 package com.iluwatar.reactor.app;
 
-import java.io.IOException;
-import java.util.ArrayList;
-import java.util.List;
-
 import com.iluwatar.reactor.framework.AbstractNioChannel;
 import com.iluwatar.reactor.framework.ChannelHandler;
 import com.iluwatar.reactor.framework.Dispatcher;
@@ -34,19 +30,20 @@ import com.iluwatar.reactor.framework.NioDatagramChannel;
 import com.iluwatar.reactor.framework.NioReactor;
 import com.iluwatar.reactor.framework.NioServerSocketChannel;
 import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 
 /**
  * This application demonstrates Reactor pattern. The example demonstrated is a Distributed Logging
  * Service where it listens on multiple TCP or UDP sockets for incoming log requests.
  *
- * <p>
+ * <p><i>INTENT</i> <br>
- * <i>INTENT</i> <br>
  * The Reactor design pattern handles service requests that are delivered concurrently to an
  * application by one or more clients. The application can register specific handlers for processing
  * which are called by reactor on specific events.
  *
- * <p>
+ * <p><i>PROBLEM</i> <br>
- * <i>PROBLEM</i> <br>
  * Server applications in a distributed system must handle multiple clients that send them service
  * requests. Following forces need to be resolved:
  * <ul>
@@ -56,8 +53,7 @@ import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
  * <li>Adaptability</li>
  * </ul>
  *
- * <p>
+ * <p><i>PARTICIPANTS</i> <br>
- * <i>PARTICIPANTS</i> <br>
  * <ul>
  * <li>Synchronous Event De-multiplexer
  * <p>
@@ -89,7 +85,6 @@ import com.iluwatar.reactor.framework.ThreadPoolDispatcher;
  * separate thread for each client, which provides better scalability under load (number of clients
  * increase).
  * The example uses Java NIO framework to implement the Reactor.
- * 
  */
 public class App {
 

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

@@ -23,9 +23,6 @@
 
 package com.iluwatar.reactor.app;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
@@ -39,6 +36,8 @@ import java.net.UnknownHostException;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * Represents the clients of Reactor pattern. Multiple clients are run concurrently and send logging

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

@@ -23,12 +23,11 @@
 
 package com.iluwatar.reactor.app;
 
-import java.nio.ByteBuffer;
-import java.nio.channels.SelectionKey;
-
 import com.iluwatar.reactor.framework.AbstractNioChannel;
 import com.iluwatar.reactor.framework.ChannelHandler;
 import com.iluwatar.reactor.framework.NioDatagramChannel.DatagramPacket;
+import java.nio.ByteBuffer;
+import java.nio.channels.SelectionKey;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -63,7 +62,11 @@ public class LoggingHandler implements ChannelHandler {
     }
   }
 
-  private static void sendReply(AbstractNioChannel channel, DatagramPacket incomingPacket, SelectionKey key) {
+  private static void sendReply(
+      AbstractNioChannel channel,
+      DatagramPacket incomingPacket,
+      SelectionKey key
+  ) {
     /*
      * Create a reply acknowledgement datagram packet setting the receiver to the sender of incoming
      * message.

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

@@ -36,12 +36,11 @@ import java.util.concurrent.ConcurrentLinkedQueue;
  * This represents the <i>Handle</i> of Reactor pattern. These are resources managed by OS which can
  * be submitted to {@link NioReactor}.
  *
- * <p>
+ * <p>This class serves has the responsibility of reading the data when a read event occurs and
- * This class serves has the responsibility of reading the data when a read event occurs and writing
+ * writing the data back when the channel is writable. It leaves the reading and writing of data on
- * the data back when the channel is writable. It leaves the reading and writing of data on the
+ * the concrete implementation. It provides a block writing mechanism wherein when any {@link
- * concrete implementation. It provides a block writing mechanism wherein when any
+ * ChannelHandler} wants to write data back, it queues the data in pending write queue and clears it
- * {@link ChannelHandler} wants to write data back, it queues the data in pending write queue and
+ * in block manner. This provides better throughput.
- * clears it in block manner. This provides better throughput.
  */
 public abstract class AbstractNioChannel {
 
@@ -70,6 +69,8 @@ public abstract class AbstractNioChannel {
   }
 
   /**
+   * Get channel.
+   *
    * @return the wrapped NIO channel.
    */
   public SelectableChannel getJavaChannel() {
@@ -77,8 +78,8 @@ public abstract class AbstractNioChannel {
   }
 
   /**
-   * The operation in which the channel is interested, this operation is provided to
+   * The operation in which the channel is interested, this operation is provided to {@link
-   * {@link Selector}.
+   * Selector}.
    *
    * @return interested operation.
    * @see SelectionKey
@@ -103,6 +104,8 @@ public abstract class AbstractNioChannel {
   public abstract Object read(SelectionKey key) throws IOException;
 
   /**
+   * Get handler.
+   *
    * @return the handler associated with this channel.
    */
   public ChannelHandler getHandler() {
@@ -141,15 +144,14 @@ public abstract class AbstractNioChannel {
    * Queues the data for writing. The data is not guaranteed to be written on underlying channel
    * when this method returns. It will be written when the channel is flushed.
    *
-   * <p>
+   * <p>This method is used by the {@link ChannelHandler} to send reply back to the client. <br>
-   * This method is used by the {@link ChannelHandler} to send reply back to the client. <br>
    * Example:
    *
    * <pre>
    * <code>
    * {@literal @}Override
-   * public void handleChannelRead(AbstractNioChannel channel, Object readObject, SelectionKey key) {
+   * public void handleChannelRead(AbstractNioChannel channel, Object readObj, SelectionKey key) {
-   *   byte[] data = ((ByteBuffer)readObject).array();
+   *   byte[] data = ((ByteBuffer)readObj).array();
    *   ByteBuffer buffer = ByteBuffer.wrap("Server reply".getBytes());
    *   channel.write(buffer, key);
    * }

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

@@ -29,9 +29,9 @@ import java.nio.channels.SelectionKey;
  * Represents the <i>EventHandler</i> of Reactor pattern. It handles the incoming events dispatched
  * to it by the {@link Dispatcher}. This is where the application logic resides.
  *
- * <p>
+ * <p>A {@link ChannelHandler} can be associated with one or many {@link AbstractNioChannel}s, and
- * A {@link ChannelHandler} can be associated with one or many {@link AbstractNioChannel}s, and
+ * whenever an event occurs on any of the associated channels, the handler is notified of the
- * whenever an event occurs on any of the associated channels, the handler is notified of the event.
+ * event.
  */
 public interface ChannelHandler {
 

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

@@ -29,12 +29,10 @@ import java.nio.channels.SelectionKey;
  * Represents the event dispatching strategy. When {@link NioReactor} senses any event on the
  * registered {@link AbstractNioChannel}s then it de-multiplexes the event type, read or write or
  * connect, and then calls the {@link Dispatcher} to dispatch the read events. This decouples the
- * I/O processing from application specific processing. <br>
+ * I/O processing from application specific processing. <br> Dispatcher should call the {@link
- * Dispatcher should call the {@link ChannelHandler} associated with the channel on which event
+ * ChannelHandler} associated with the channel on which event occurred.
- * occurred.
  *
- * <p>
+ * <p>The application can customize the way in which event is dispatched such as using the reactor
- * The application can customize the way in which event is dispatched such as using the reactor
  * thread to dispatch event to channels or use a worker pool to do the non I/O processing.
  *
  * @see SameThreadDispatcher
@@ -46,8 +44,7 @@ public interface Dispatcher {
    * provided in <code>readObject</code>. The implementation should dispatch this read event to the
    * associated {@link ChannelHandler} of <code>channel</code>.
    *
-   * <p>
+   * <p>The type of <code>readObject</code> depends on the channel on which data was received.
-   * The type of <code>readObject</code> depends on the channel on which data was received.
    *
    * @param channel    on which read event occurred
    * @param readObject object read by channel

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

@@ -23,9 +23,6 @@
 
 package com.iluwatar.reactor.framework;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.io.IOException;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -33,6 +30,8 @@ import java.net.SocketAddress;
 import java.nio.ByteBuffer;
 import java.nio.channels.DatagramChannel;
 import java.nio.channels.SelectionKey;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
  * A wrapper over {@link DatagramChannel} which can read and write data on a DatagramChannel.
@@ -46,8 +45,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
   /**
    * Creates a {@link DatagramChannel} which will bind at provided port and use <code>handler</code>
    * to handle incoming events on this channel.
-   * <p>
+   *
-   * Note the constructor does not bind the socket, {@link #bind()} method should be called for
+   * <p>Note the constructor does not bind the socket, {@link #bind()} method should be called for
    * binding the socket.
    *
    * @param port    the port to be bound to listen for incoming datagram requests.
@@ -89,6 +88,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
   }
 
   /**
+   * Get datagram channel.
+   *
    * @return the underlying datagram channel.
    */
   @Override
@@ -120,8 +121,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
 
   /**
    * Writes the outgoing {@link DatagramPacket} to the channel. The intended receiver of the
-   * datagram packet must be set in the <code>data</code> using
+   * datagram packet must be set in the <code>data</code> using {@link
-   * {@link DatagramPacket#setReceiver(SocketAddress)}.
+   * DatagramPacket#setReceiver(SocketAddress)}.
    */
   @Override
   public void write(Object data, SelectionKey key) {
@@ -146,6 +147,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
     }
 
     /**
+     * Get sender address.
+     *
      * @return the sender address.
      */
     public SocketAddress getSender() {
@@ -162,6 +165,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
     }
 
     /**
+     * Get receiver address.
+     *
      * @return the receiver address.
      */
     public SocketAddress getReceiver() {
@@ -178,6 +183,8 @@ public class NioDatagramChannel extends AbstractNioChannel {
     }
 
     /**
+     * Get data.
+     *
      * @return the underlying message that will be written on channel.
      */
     public ByteBuffer getData() {

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

@@ -23,9 +23,6 @@
 
 package com.iluwatar.reactor.framework;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.io.IOException;
 import java.nio.channels.SelectionKey;
 import java.nio.channels.Selector;
@@ -38,22 +35,23 @@ import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ExecutorService;
 import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
- * This class acts as Synchronous Event De-multiplexer and Initiation Dispatcher of Reactor pattern. Multiple handles
+ * This class acts as Synchronous Event De-multiplexer and Initiation Dispatcher of Reactor pattern.
- * i.e. {@link AbstractNioChannel}s can be registered to the reactor and it blocks for events from all these handles.
+ * Multiple handles i.e. {@link AbstractNioChannel}s can be registered to the reactor and it blocks
- * Whenever an event occurs on any of the registered handles, it synchronously de-multiplexes the event which can be any
+ * for events from all these handles. Whenever an event occurs on any of the registered handles, it
- * of read, write or accept, and dispatches the event to the appropriate {@link ChannelHandler} using the
+ * synchronously de-multiplexes the event which can be any of read, write or accept, and dispatches
- * {@link Dispatcher}.
+ * the event to the appropriate {@link ChannelHandler} using the {@link Dispatcher}.
  *
- * <p>
+ * <p>Implementation: A NIO reactor runs in its own thread when it is started using {@link
- * Implementation: A NIO reactor runs in its own thread when it is started using {@link #start()} method.
+ * #start()} method. {@link NioReactor} uses {@link Selector} for realizing Synchronous Event
- * {@link NioReactor} uses {@link Selector} for realizing Synchronous Event De-multiplexing.
+ * De-multiplexing.
  *
- * <p>
+ * <p>NOTE: This is one of the ways to implement NIO reactor and it does not take care of all
- * NOTE: This is one of the ways to implement NIO reactor and it does not take care of all possible edge cases which are
+ * possible edge cases which are required in a real application. This implementation is meant to
- * required in a real application. This implementation is meant to demonstrate the fundamental concepts that lie behind
+ * demonstrate the fundamental concepts that lie behind Reactor pattern.
- * Reactor pattern.
  */
 public class NioReactor {
 
@@ -62,21 +60,20 @@ public class NioReactor {
   private final Selector selector;
   private final Dispatcher dispatcher;
   /**
-   * All the work of altering the SelectionKey operations and Selector operations are performed in the context of main
+   * All the work of altering the SelectionKey operations and Selector operations are performed in
-   * event loop of reactor. So when any channel needs to change its readability or writability, a new command is added
+   * the context of main event loop of reactor. So when any channel needs to change its readability
-   * in the command queue and then the event loop picks up the command and executes it in next iteration.
+   * or writability, a new command is added in the command queue and then the event loop picks up
+   * the command and executes it in next iteration.
    */
   private final Queue<Runnable> pendingCommands = new ConcurrentLinkedQueue<>();
   private final ExecutorService reactorMain = Executors.newSingleThreadExecutor();
 
   /**
-   * Creates a reactor which will use provided {@code dispatcher} to dispatch events. The application can provide
+   * Creates a reactor which will use provided {@code dispatcher} to dispatch events. The
-   * various implementations of dispatcher which suits its needs.
+   * application can provide various implementations of dispatcher which suits its needs.
    *
-   * @param dispatcher
+   * @param dispatcher a non-null dispatcher used to dispatch events on registered channels.
-   *          a non-null dispatcher used to dispatch events on registered channels.
+   * @throws IOException if any I/O error occurs.
-   * @throws IOException
-   *           if any I/O error occurs.
    */
   public NioReactor(Dispatcher dispatcher) throws IOException {
     this.dispatcher = dispatcher;
@@ -100,10 +97,8 @@ public class NioReactor {
   /**
    * Stops the reactor and related resources such as dispatcher.
    *
-   * @throws InterruptedException
+   * @throws InterruptedException if interrupted while stopping the reactor.
-   *           if interrupted while stopping the reactor.
+   * @throws IOException          if any I/O error occurs.
-   * @throws IOException
-   *           if any I/O error occurs.
    */
   public void stop() throws InterruptedException, IOException {
     reactorMain.shutdownNow();
@@ -114,15 +109,14 @@ public class NioReactor {
   }
 
   /**
-   * Registers a new channel (handle) with this reactor. Reactor will start waiting for events on this channel and
+   * Registers a new channel (handle) with this reactor. Reactor will start waiting for events on
-   * notify of any events. While registering the channel the reactor uses {@link AbstractNioChannel#getInterestedOps()}
+   * this channel and notify of any events. While registering the channel the reactor uses {@link
-   * to know about the interested operation of this channel.
+   * AbstractNioChannel#getInterestedOps()} to know about the interested operation of this channel.
    *
-   * @param channel
+   * @param channel a new channel on which reactor will wait for events. The channel must be bound
-   *          a new channel on which reactor will wait for events. The channel must be bound prior to being registered.
+   *                prior to being registered.
    * @return this
-   * @throws IOException
+   * @throws IOException if any I/O error occurs.
-   *           if any I/O error occurs.
    */
   public NioReactor registerChannel(AbstractNioChannel channel) throws IOException {
     SelectionKey key = channel.getJavaChannel().register(selector, channel.getInterestedOps());
@@ -143,8 +137,8 @@ public class NioReactor {
       processPendingCommands();
 
       /*
-       * Synchronous event de-multiplexing happens here, this is blocking call which returns when it is possible to
+       * Synchronous event de-multiplexing happens here, this is blocking call which returns when it
-       * initiate non-blocking operation on any of the registered channels.
+       * is possible to initiate non-blocking operation on any of the registered channels.
        */
       selector.select();
 
@@ -177,8 +171,8 @@ public class NioReactor {
   }
 
   /*
-   * Initiation dispatcher logic, it checks the type of event and notifier application specific event handler to handle
+   * Initiation dispatcher logic, it checks the type of event and notifier application specific
-   * the event.
+   * event handler to handle the event.
    */
   private void processKey(SelectionKey key) throws IOException {
     if (key.isAcceptable()) {
@@ -226,15 +220,14 @@ public class NioReactor {
   }
 
   /**
-   * Queues the change of operations request of a channel, which will change the interested operations of the channel
+   * Queues the change of operations request of a channel, which will change the interested
-   * sometime in future.
+   * operations of the channel sometime in future.
-   * <p>
-   * This is a non-blocking method and does not guarantee that the operations have changed when this method returns.
    *
-   * @param key
+   * <p>This is a non-blocking method and does not guarantee that the operations have changed when
-   *          the key for which operations have to be changed.
+   * this method returns.
-   * @param interestedOps
+   *
-   *          the new interest operations.
+   * @param key           the key for which operations have to be changed.
+   * @param interestedOps the new interest operations.
    */
   public void changeOps(SelectionKey key, int interestedOps) {
     pendingCommands.add(new ChangeKeyOpsCommand(key, interestedOps));

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

@@ -23,9 +23,6 @@
 
 package com.iluwatar.reactor.framework;
 
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
 import java.io.IOException;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
@@ -33,10 +30,12 @@ import java.nio.ByteBuffer;
 import java.nio.channels.SelectionKey;
 import java.nio.channels.ServerSocketChannel;
 import java.nio.channels.SocketChannel;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
 
 /**
- * A wrapper over {@link NioServerSocketChannel} which can read and write data on a
+ * A wrapper over {@link NioServerSocketChannel} which can read and write data on a {@link
- * {@link SocketChannel}.
+ * SocketChannel}.
  */
 public class NioServerSocketChannel extends AbstractNioChannel {
 
@@ -47,8 +46,8 @@ public class NioServerSocketChannel extends AbstractNioChannel {
   /**
    * Creates a {@link ServerSocketChannel} which will bind at provided port and use
    * <code>handler</code> to handle incoming events on this channel.
-   * <p>
+   *
-   * Note the constructor does not bind the socket, {@link #bind()} method should be called for
+   * <p>Note the constructor does not bind the socket, {@link #bind()} method should be called for
    * binding the socket.
    *
    * @param port    the port on which channel will be bound to accept incoming connection requests.
@@ -68,6 +67,8 @@ public class NioServerSocketChannel extends AbstractNioChannel {
   }
 
   /**
+   * Get server socket channel.
+   *
    * @return the underlying {@link ServerSocketChannel}.
    */
   @Override

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

@@ -30,17 +30,15 @@ import java.nio.channels.SelectionKey;
  * small applications where there are limited clients. Using this implementation limits the
  * scalability because the I/O thread performs the application specific processing.
  *
- * <p>
+ * <p>For better performance use {@link ThreadPoolDispatcher}.
- * For better performance use {@link ThreadPoolDispatcher}.
  *
  * @see ThreadPoolDispatcher
  */
 public class SameThreadDispatcher implements Dispatcher {
 
   /**
-   * Dispatches the read event in the context of caller thread. <br>
+   * Dispatches the read event in the context of caller thread. <br> Note this is a blocking call.
-   * Note this is a blocking call. It returns only after the associated handler has handled the read
+   * It returns only after the associated handler has handled the read event.
-   * event.
    */
   @Override
   public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) {

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

@@ -48,9 +48,8 @@ public class ThreadPoolDispatcher implements Dispatcher {
 
   /**
    * Submits the work of dispatching the read event to worker pool, where it gets picked up by
-   * worker threads. <br>
+   * worker threads. <br> Note that this is a non-blocking call and returns immediately. It is not
-   * Note that this is a non-blocking call and returns immediately. It is not guaranteed that the
+   * guaranteed that the event has been handled by associated handler.
-   * event has been handled by associated handler.
    */
   @Override
   public void onChannelReadEvent(AbstractNioChannel channel, Object readObject, SelectionKey key) {

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

@@ -28,25 +28,22 @@ 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;
 
 /**
- * 
  * In a multiple thread applications, the threads may try to synchronize the shared resources
  * regardless of read or write operation. It leads to a low performance especially in a "read more
  * write less" system as indeed the read operations are thread-safe to another read operation.
- * <p>
- * Reader writer lock is a synchronization primitive that try to resolve this problem. This pattern
- * allows concurrent access for read-only operations, while write operations require exclusive
- * access. This means that multiple threads can read the data in parallel but an exclusive lock is
- * needed for writing or modifying data. When a writer is writing the data, all other writers or
- * readers will be blocked until the writer is finished writing.
  *
- * <p>
+ * <p>Reader writer lock is a synchronization primitive that try to resolve this problem. This
- * This example use two mutex to demonstrate the concurrent access of multiple readers and writers.
+ * pattern allows concurrent access for read-only operations, while write operations require
+ * exclusive access. This means that multiple threads can read the data in parallel but an exclusive
+ * lock is needed for writing or modifying data. When a writer is writing the data, all other
+ * writers or readers will be blocked until the writer is finished writing.
  *
+ * <p>This example use two mutex to demonstrate the concurrent access of multiple readers and
+ * writers.
  *
  * @author hongshuwei@gmail.com
  */
@@ -55,7 +52,7 @@ public class App {
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
 
   /**
-   * Program entry point
+   * Program entry point.
    *
    * @param args command line args
    */
@@ -90,7 +87,6 @@ public class App {
     LOGGER.info("More readers added...");
 
 
-
     // In the system console, it can see that the read operations are executed concurrently while
     // write operations are exclusive.
     executeService.shutdown();

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

@@ -24,12 +24,11 @@
 package com.iluwatar.reader.writer.lock;
 
 import java.util.concurrent.locks.Lock;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * Reader class, read when it acquired the read lock
+ * Reader class, read when it acquired the read lock.
  */
 public class Reader implements Runnable {
 
@@ -42,7 +41,7 @@ public class Reader implements Runnable {
   private long readingTime;
 
   /**
-   * Create new Reader
+   * Create new Reader.
    *
    * @param name        - Name of the thread owning the reader
    * @param readLock    - Lock for this reader
@@ -55,7 +54,7 @@ public class Reader implements Runnable {
   }
 
   /**
-   * Create new Reader who reads for 250ms
+   * Create new Reader who reads for 250ms.
    *
    * @param name     - Name of the thread owning the reader
    * @param readLock - Lock for this reader
@@ -78,8 +77,7 @@ public class Reader implements Runnable {
   }
 
   /**
-   * Simulate the read operation
+   * Simulate the read operation.
-   * 
    */
   public void read() throws InterruptedException {
     LOGGER.info("{} begin", name);

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

@@ -29,15 +29,14 @@ import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Condition;
 import java.util.concurrent.locks.Lock;
 import java.util.concurrent.locks.ReadWriteLock;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
  * Class responsible for control the access for reader or writer
  *
- * Allows multiple readers to hold the lock at same time, but if any writer holds the lock then readers wait. If reader
+ * <p>Allows multiple readers to hold the lock at same time, but if any writer holds the lock then
- * holds the lock then writer waits. This lock is not fair.
+ * readers wait. If reader holds the lock then writer waits. This lock is not fair.
  */
 public class ReaderWriterLock implements ReadWriteLock {
 
@@ -50,13 +49,13 @@ public class ReaderWriterLock implements ReadWriteLock {
 
   /**
    * Global mutex is used to indicate that whether reader or writer gets the lock in the moment.
-   * <p>
+   *
-   * 1. When it contains the reference of {@link #readerLock}, it means that the lock is acquired by the reader, another
+   * <p>1. When it contains the reference of {@link #readerLock}, it means that the lock is
-   * reader can also do the read operation concurrently. <br>
+   * acquired by the reader, another reader can also do the read operation concurrently. <br> 2.
-   * 2. When it contains the reference of reference of {@link #writerLock}, it means that the lock is acquired by the
+   * When it contains the reference of reference of {@link #writerLock}, it means that the lock is
-   * writer exclusively, no more reader or writer can get the lock.
+   * acquired by the writer exclusively, no more reader or writer can get the lock.
-   * <p>
+   *
-   * This is the most important field in this class to control the access for reader/writer.
+   * <p>This is the most important field in this class to control the access for reader/writer.
    */
   private Set<Object> globalMutex = new HashSet<>();
 
@@ -74,22 +73,21 @@ public class ReaderWriterLock implements ReadWriteLock {
   }
 
   /**
-   * return true when globalMutex hold the reference of writerLock
+   * return true when globalMutex hold the reference of writerLock.
    */
   private boolean doesWriterOwnThisLock() {
     return globalMutex.contains(writerLock);
   }
 
   /**
-   * Nobody get the lock when globalMutex contains nothing
+   * Nobody get the lock when globalMutex contains nothing.
-   * 
    */
   private boolean isLockFree() {
     return globalMutex.isEmpty();
   }
 
   /**
-   * Reader Lock, can be access for more than one reader concurrently if no writer get the lock
+   * Reader Lock, can be access for more than one reader concurrently if no writer get the lock.
    */
   private class ReadLock implements Lock {
 
@@ -104,8 +102,8 @@ public class ReaderWriterLock implements ReadWriteLock {
     }
 
     /**
-     * Acquire the globalMutex lock on behalf of current and future concurrent readers. Make sure no writers currently
+     * Acquire the globalMutex lock on behalf of current and future concurrent readers. Make sure no
-     * owns the lock.
+     * writers currently owns the lock.
      */
     private void acquireForReaders() {
       // Try to get the globalMutex lock for the first reader
@@ -116,7 +114,8 @@ public class ReaderWriterLock implements ReadWriteLock {
           try {
             globalMutex.wait();
           } catch (InterruptedException e) {
-            LOGGER.info("InterruptedException while waiting for globalMutex in acquireForReaders", e);
+            LOGGER
+                .info("InterruptedException while waiting for globalMutex in acquireForReaders", e);
             Thread.currentThread().interrupt();
           }
         }
@@ -165,7 +164,7 @@ public class ReaderWriterLock implements ReadWriteLock {
   }
 
   /**
-   * Writer Lock, can only be accessed by one writer concurrently
+   * Writer Lock, can only be accessed by one writer concurrently.
    */
   private class WriteLock implements Lock {
 

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

@@ -24,12 +24,11 @@
 package com.iluwatar.reader.writer.lock;
 
 import java.util.concurrent.locks.Lock;
-
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * Writer class, write when it acquired the write lock
+ * Writer class, write when it acquired the write lock.
  */
 public class Writer implements Runnable {
 
@@ -42,7 +41,7 @@ public class Writer implements Runnable {
   private long writingTime;
 
   /**
-   * Create new Writer who writes for 250ms
+   * Create new Writer who writes for 250ms.
    *
    * @param name      - Name of the thread owning the writer
    * @param writeLock - Lock for this writer
@@ -52,7 +51,7 @@ public class Writer implements Runnable {
   }
 
   /**
-   * Create new Writer
+   * Create new Writer.
    *
    * @param name        - Name of the thread owning the writer
    * @param writeLock   - Lock for this writer
@@ -79,7 +78,7 @@ public class Writer implements Runnable {
   }
 
   /**
-   * Simulate the write operation
+   * Simulate the write operation.
    */
   public void write() throws InterruptedException {
     LOGGER.info("{} begin", name);

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

@@ -25,7 +25,6 @@ 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;
@@ -38,8 +37,8 @@ import org.springframework.context.support.ClassPathXmlApplicationContext;
  * query construction code is concentrated. This becomes more important when there are a large
  * number of domain classes or heavy querying. In these cases particularly, adding this layer helps
  * minimize duplicate query logic.
- * <p>
+ *
- * In this example we utilize Spring Data to automatically generate a repository for us from the
+ * <p>In this example we utilize Spring Data to automatically generate a repository for us from the
  * {@link Person} domain object. Using the {@link PersonRepository} we perform CRUD operations on
  * the entity, moreover, the query by {@link org.springframework.data.jpa.domain.Specification} are
  * also performed. Underneath we have configured in-memory H2 database for which schema is created
@@ -50,10 +49,9 @@ public class App {
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
 
   /**
-   * Program entry point
+   * Program entry point.
    *
-   * @param args
+   * @param args command line args
-   *          command line args
    */
   public static void main(String[] args) {
 

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

@@ -27,9 +27,7 @@ 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;
 import org.hibernate.jpa.HibernatePersistenceProvider;
 import org.slf4j.Logger;
@@ -42,9 +40,7 @@ import org.springframework.orm.jpa.JpaTransactionManager;
 import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
 
 /**
- * This is the same example as in {@link App} but with annotations based 
+ * This is the same example as in {@link App} but with annotations based configuration for Spring.
- * configuration for Spring.
- *
  */
 @EnableJpaRepositories
 @SpringBootConfiguration
@@ -53,7 +49,7 @@ public class AppConfig {
   private static final Logger LOGGER = LoggerFactory.getLogger(AppConfig.class);
 
   /**
-   * Creation of H2 db
+   * Creation of H2 db.
    *
    * @return A new Instance of DataSource
    */
@@ -68,11 +64,12 @@ public class AppConfig {
   }
 
   /**
-   * Factory to create a especific instance of Entity Manager
+   * Factory to create a especific instance of Entity Manager.
    */
   @Bean
   public LocalContainerEntityManagerFactoryBean entityManagerFactory() {
-    LocalContainerEntityManagerFactoryBean entityManager = new LocalContainerEntityManagerFactoryBean();
+    LocalContainerEntityManagerFactoryBean entityManager =
+        new LocalContainerEntityManagerFactoryBean();
     entityManager.setDataSource(dataSource());
     entityManager.setPackagesToScan("com.iluwatar");
     entityManager.setPersistenceProvider(new HibernatePersistenceProvider());
@@ -82,7 +79,7 @@ public class AppConfig {
   }
 
   /**
-   * Properties for Jpa
+   * Properties for Jpa.
    */
   private static Properties jpaProperties() {
     Properties properties = new Properties();
@@ -92,7 +89,7 @@ public class AppConfig {
   }
 
   /**
-   * Get transaction manager
+   * Get transaction manager.
    */
   @Bean
   public JpaTransactionManager transactionManager() throws SQLException {
@@ -102,10 +99,9 @@ public class AppConfig {
   }
 
   /**
-   * Program entry point
+   * Program entry point.
    *
-   * @param args
+   * @param args command line args
-   *          command line args
    */
   public static void main(String[] args) {
 

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

@@ -28,9 +28,7 @@ import javax.persistence.GeneratedValue;
 import javax.persistence.Id;
 
 /**
- * 
+ * Person entity.
- * Person entity
- *
  */
 @Entity
 public class Person {
@@ -47,7 +45,7 @@ public class Person {
   }
 
   /**
-   * Constructor
+   * Constructor.
    */
   public Person(String name, String surname, int age) {
     this.name = name;

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

@@ -28,9 +28,7 @@ import org.springframework.data.repository.CrudRepository;
 import org.springframework.stereotype.Repository;
 
 /**
- * 
+ * Person repository.
- * Person repository
- *
  */
 @Repository
 public interface PersonRepository

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

@@ -27,16 +27,15 @@ import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
-
 import org.springframework.data.jpa.domain.Specification;
 
 /**
- * Helper class, includes vary Specification as the abstraction of sql query criteria
+ * Helper class, includes vary Specification as the abstraction of sql query criteria.
  */
 public class PersonSpecifications {
 
   /**
-   * Specifications stating the Between (From - To) Age Specification
+   * Specifications stating the Between (From - To) Age Specification.
    */
   public static class AgeBetweenSpec implements Specification<Person> {
 
@@ -59,8 +58,7 @@ public class PersonSpecifications {
   }
 
   /**
-   * Name specification
+   * Name specification.
-   *
    */
   public static class NameEqualSpec implements Specification<Person> {
 
@@ -71,7 +69,7 @@ public class PersonSpecifications {
     }
 
     /**
-     * Get predicate
+     * Get predicate.
      */
     public Predicate toPredicate(Root<Person> root, CriteriaQuery<?> query, CriteriaBuilder cb) {
 

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

@@ -27,31 +27,30 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * 
  * Resource Acquisition Is Initialization pattern was developed for exception safe resource
  * management by C++ creator Bjarne Stroustrup.
- * <p>
- * In RAII resource is tied to object lifetime: resource allocation is done during object creation
- * while resource deallocation is done during object destruction.
- * <p>
- * In Java RAII is achieved with try-with-resources statement and interfaces {@link java.io.Closeable} and
- * {@link AutoCloseable}. The try-with-resources statement ensures that each resource is closed at
- * the end of the statement. Any object that implements {@link java.lang.AutoCloseable}, which
- * includes all objects which implement {@link java.io.Closeable}, can be used as a resource.
  *
- * In this example, {@link SlidingDoor} implements {@link AutoCloseable} and {@link TreasureChest}
+ * <p>In RAII resource is tied to object lifetime: resource allocation is done during object
- * implements {@link java.io.Closeable}. Running the example, we can observe that both resources are
+ * creation while resource deallocation is done during object destruction.
- * automatically closed.
- * <p>
- * http://docs.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html
  *
+ * <p>In Java RAII is achieved with try-with-resources statement and interfaces {@link
+ * java.io.Closeable} and {@link AutoCloseable}. The try-with-resources statement ensures that each
+ * resource is closed at the end of the statement. Any object that implements {@link
+ * java.lang.AutoCloseable}, which includes all objects which implement {@link java.io.Closeable},
+ * can be used as a resource.
+ *
+ * <p>In this example, {@link SlidingDoor} implements {@link AutoCloseable} and {@link
+ * TreasureChest} implements {@link java.io.Closeable}. Running the example, we can observe that
+ * both resources are automatically closed.
+ *
+ * <p>http://docs.oracle.com/javase/7/docs/technotes/guides/language/try-with-resources.html
  */
 public class App {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
 
   /**
-   * Program entry point
+   * Program entry point.
    */
   public static void main(String[] args) throws Exception {
 

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

@@ -27,9 +27,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /**
- * 
+ * SlidingDoor resource.
- * SlidingDoor resource
- *
  */
 public class SlidingDoor implements AutoCloseable {
 

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

@@ -23,16 +23,13 @@
 
 package com.iluwatar.resource.acquisition.is.initialization;
 
+import java.io.Closeable;
+import java.io.IOException;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import java.io.Closeable;
-import java.io.IOException;
-
 /**
- * 
+ * TreasureChest resource.
- * TreasureChest resource
- *
  */
 public class TreasureChest implements Closeable {
 

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

@@ -31,30 +31,31 @@ import org.slf4j.LoggerFactory;
  * the environment if the business requirements and nature of the failures allow it. By retrying
  * failed operations on external dependencies, the application may maintain stability and minimize
  * negative impact on the user experience.
- * <p>
+ *
- * In our example, we have the {@link BusinessOperation} interface as an abstraction over
+ * <p>In our example, we have the {@link BusinessOperation} interface as an abstraction over all
- * all operations that our application performs involving remote systems. The calling code should
+ * operations that our application performs involving remote systems. The calling code should remain
- * remain decoupled from implementations. 
+ * decoupled from implementations.
- * <p>
+ *
- * {@link FindCustomer} is a business operation that looks up a customer's record and returns 
+ * <p>{@link FindCustomer} is a business operation that looks up a customer's record and returns
  * its ID. Imagine its job is performed by looking up the customer in our local database and
- * returning its ID. We can pass {@link CustomerNotFoundException} as one of its 
+ * returning its ID. We can pass {@link CustomerNotFoundException} as one of its {@link
- * {@link FindCustomer#FindCustomer(java.lang.String, com.iluwatar.retry.BusinessException...) 
+ * FindCustomer#FindCustomer(java.lang.String, com.iluwatar.retry.BusinessException...) constructor
- * constructor parameters} in order to simulate not finding the customer.
+ * parameters} in order to simulate not finding the customer.
- * <p>
+ *
- * Imagine that, lately, this operation has experienced intermittent failures due to some weird 
+ * <p>Imagine that, lately, this operation has experienced intermittent failures due to some weird
  * corruption and/or locking in the data. After retrying a few times the customer is found. The
  * database is still, however, expected to always be available.  While a definitive solution is
- * found to the problem, our engineers advise us to retry the operation a set number
+ * found to the problem, our engineers advise us to retry the operation a set number of times with a
- * of times with a set delay between retries, although not too many retries otherwise the end user
+ * set delay between retries, although not too many retries otherwise the end user will be left
- * will be left waiting for a long time, while delays that are too short will not allow the database
+ * waiting for a long time, while delays that are too short will not allow the database to recover
- * to recover from the load. 
+ * from the load.
- * <p>
+ *
- * To keep the calling code as decoupled as possible from this workaround, we have implemented the
+ * <p>To keep the calling code as decoupled as possible from this workaround, we have implemented
- * retry mechanism as a {@link BusinessOperation} named {@link Retry}.
+ * the retry mechanism as a {@link BusinessOperation} named {@link Retry}.
  *
  * @author George Aristy (george.aristy@gmail.com)
- * @see <a href="https://docs.microsoft.com/en-us/azure/architecture/patterns/retry">Retry pattern (Microsoft Azure Docs)</a>
+ * @see <a href="https://docs.microsoft.com/en-us/azure/architecture/patterns/retry">Retry pattern
+ *     (Microsoft Azure Docs)</a>
  */
 public final class App {
   private static final Logger LOG = LoggerFactory.getLogger(App.class);

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

@@ -24,10 +24,10 @@
 package com.iluwatar.retry;
 
 /**
- * The top-most type in our exception hierarchy that signifies that an unexpected error 
+ * The top-most type in our exception hierarchy that signifies that an unexpected error condition
- * condition occurred. Its use is reserved as a "catch-all" for cases where no other subtype 
+ * occurred. Its use is reserved as a "catch-all" for cases where no other subtype captures the
- * captures the specificity of the error condition in question. Calling code is not expected to 
+ * specificity of the error condition in question. Calling code is not expected to be able to handle
- * be able to handle this error and should be reported to the maintainers immediately.
+ * this error and should be reported to the maintainers immediately.
  *
  * @author George Aristy (george.aristy@gmail.com)
  */
@@ -35,7 +35,7 @@ public class BusinessException extends Exception {
   private static final long serialVersionUID = 6235833142062144336L;
 
   /**
-   * Ctor
+   * Ctor.
    *
    * @param message the error message
    */

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

@@ -26,8 +26,8 @@ package com.iluwatar.retry;
 /**
  * Performs some business operation.
  *
- * @author George Aristy (george.aristy@gmail.com)
  * @param <T> the return type
+ * @author George Aristy (george.aristy@gmail.com)
  */
 @FunctionalInterface
 public interface BusinessOperation<T> {

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

@@ -25,9 +25,10 @@ package com.iluwatar.retry;
 
 /**
  * Indicates that the customer was not found.
- * <p>
+ *
- * The severity of this error is bounded by its context: was the search for the customer triggered
+ * <p>The severity of this error is bounded by its context: was the search for the customer
- * by an input from some end user, or were the search parameters pulled from your database?
+ * triggered by an input from some end user, or were the search parameters pulled from your
+ * database?
  *
  * @author George Aristy (george.aristy@gmail.com)
  */

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

@@ -29,8 +29,8 @@ import java.util.List;
 
 /**
  * Finds a customer, returning its ID from our records.
- * <p>
+ *
- * This is an imaginary operation that, for some imagined input, returns the ID for a customer. 
+ * <p>This is an imaginary operation that, for some imagined input, returns the ID for a customer.
  * However, this is a "flaky" operation that is supposed to fail intermittently, but for the
  * purposes of this example it fails in a programmed way depending on the constructor parameters.
  *

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

@@ -33,8 +33,8 @@ import java.util.function.Predicate;
 /**
  * Decorates {@link BusinessOperation business operation} with "retry" capabilities.
  *
- * @author George Aristy (george.aristy@gmail.com)
  * @param <T> the remote op's return type
+ * @author George Aristy (george.aristy@gmail.com)
  */
 public final class Retry<T> implements BusinessOperation<T> {
   private final BusinessOperation<T> op;
@@ -104,7 +104,6 @@ public final class Retry<T> implements BusinessOperation<T> {
           //ignore
         }
       }
-    }
+    } while (true);
-    while (true);
   }
 }

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

@@ -34,8 +34,8 @@ import java.util.function.Predicate;
 /**
  * Decorates {@link BusinessOperation business operation} with "retry" capabilities.
  *
- * @author George Aristy (george.aristy@gmail.com)
  * @param <T> the remote op's return type
+ * @author George Aristy (george.aristy@gmail.com)
  */
 public final class RetryExponentialBackoff<T> implements BusinessOperation<T> {
   private static final Random RANDOM = new Random();
@@ -107,8 +107,7 @@ public final class RetryExponentialBackoff<T> implements BusinessOperation<T> {
           //ignore
         }
       }
-    }
+    } while (true);
-    while (true);
   }
 }