Code cleanup (#1461)

* Code cleanup

* Fix flux tests

* Fix checkstyle errors

* Fix compile error

double-buffer/src/main/java/com/iluwatar/doublebuffer/FrameBuffer.java

@@ -33,7 +33,7 @@ public class FrameBuffer implements Buffer {
   public static final int WIDTH = 10;
   public static final int HEIGHT = 8;
 
-  private Pixel[] pixels = new Pixel[WIDTH * HEIGHT];
+  private final Pixel[] pixels = new Pixel[WIDTH * HEIGHT];
 
   public FrameBuffer() {
     clearAll();

double-buffer/src/main/java/com/iluwatar/doublebuffer/Pixel.java

@@ -31,7 +31,7 @@ public enum Pixel {
   WHITE(0),
   BLACK(1);
 
-  private int color;
+  private final int color;
 
   Pixel(int color) {
     this.color = color;

double-buffer/src/main/java/com/iluwatar/doublebuffer/Scene.java

@@ -35,7 +35,7 @@ public class Scene {
 
   private static final Logger LOGGER = LoggerFactory.getLogger(Scene.class);
 
-  private Buffer[] frameBuffers;
+  private final Buffer[] frameBuffers;
 
   private int current;