Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

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

@@ -89,8 +89,8 @@ import java.util.List;
 public class App {
 
   private NioReactor reactor;
-  private List<AbstractNioChannel> channels = new ArrayList<>();
-  private Dispatcher dispatcher;
+  private final List<AbstractNioChannel> channels = new ArrayList<>();
+  private final Dispatcher dispatcher;
 
   /**
    * Creates an instance of App which will use provided dispatcher for dispatching events on

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

@@ -134,7 +134,7 @@ public class NioDatagramChannel extends AbstractNioChannel {
    */
   public static class DatagramPacket {
     private SocketAddress sender;
-    private ByteBuffer data;
+    private final ByteBuffer data;
     private SocketAddress receiver;
 
     /**

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

@@ -228,8 +228,8 @@ public class NioReactor {
    * A command that changes the interested operations of the key provided.
    */
   class ChangeKeyOpsCommand implements Runnable {
-    private SelectionKey key;
-    private int interestedOps;
+    private final SelectionKey key;
+    private final int interestedOps;
 
     public ChangeKeyOpsCommand(SelectionKey key, int interestedOps) {
       this.key = key;