docs: explanation for reactor (#2960)

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

@@ -52,8 +52,7 @@ public class LoggingHandler implements ChannelHandler {
     if (readObject instanceof ByteBuffer) {
       doLogging((ByteBuffer) readObject);
       sendReply(channel, key);
-    } else if (readObject instanceof DatagramPacket) {
-      var datagram = (DatagramPacket) readObject;
+    } else if (readObject instanceof DatagramPacket datagram) {
       doLogging(datagram.getData());
       sendReply(channel, datagram, key);
     } else {

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

@@ -32,6 +32,7 @@ import java.util.Map;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedQueue;
+import lombok.Getter;
 
 /**
  * This represents the <i>Handle</i> of Reactor pattern. These are resources managed by OS which can
@@ -46,6 +47,7 @@ import java.util.concurrent.ConcurrentLinkedQueue;
 public abstract class AbstractNioChannel {
 
   private final SelectableChannel channel;
+  @Getter
   private final ChannelHandler handler;
   private final Map<SelectableChannel, Queue<Object>> channelToPendingWrites;
   private NioReactor reactor;
@@ -104,15 +106,6 @@ public abstract class AbstractNioChannel {
    */
   public abstract Object read(SelectionKey key) throws IOException;
 
-  /**
-   * Get handler.
-   *
-   * @return the handler associated with this channel.
-   */
-  public ChannelHandler getHandler() {
-    return handler;
-  }
-
   /*
    * Called from the context of reactor thread when the key becomes writable. The channel writes the
    * whole pending block of data at once.

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

@@ -31,6 +31,8 @@ import java.net.SocketAddress;
 import java.nio.ByteBuffer;
 import java.nio.channels.DatagramChannel;
 import java.nio.channels.SelectionKey;
+import lombok.Getter;
+import lombok.Setter;
 import lombok.extern.slf4j.Slf4j;
 
 /**
@@ -131,9 +133,12 @@ public class NioDatagramChannel extends AbstractNioChannel {
   /**
    * Container of data used for {@link NioDatagramChannel} to communicate with remote peer.
    */
+  @Getter
   public static class DatagramPacket {
-    private SocketAddress sender;
     private final ByteBuffer data;
+    @Setter
+    private SocketAddress sender;
+    @Setter
     private SocketAddress receiver;
 
     /**
@@ -144,50 +149,5 @@ public class NioDatagramChannel extends AbstractNioChannel {
     public DatagramPacket(ByteBuffer data) {
       this.data = data;
     }
-
-    /**
-     * Get sender address.
-     *
-     * @return the sender address.
-     */
-    public SocketAddress getSender() {
-      return sender;
-    }
-
-    /**
-     * Sets the sender address of this packet.
-     *
-     * @param sender the sender address.
-     */
-    public void setSender(SocketAddress sender) {
-      this.sender = sender;
-    }
-
-    /**
-     * Get receiver address.
-     *
-     * @return the receiver address.
-     */
-    public SocketAddress getReceiver() {
-      return receiver;
-    }
-
-    /**
-     * Sets the intended receiver address. This must be set when writing to the channel.
-     *
-     * @param receiver the receiver address.
-     */
-    public void setReceiver(SocketAddress receiver) {
-      this.receiver = receiver;
-    }
-
-    /**
-     * Get data.
-     *
-     * @return the underlying message that will be written on channel.
-     */
-    public ByteBuffer getData() {
-      return data;
-    }
   }
 }