Issue#550: double buffer pattern (#1024)

* Basic implementation

* implement double buffer

* add unit test

* add unit test

* Add Readme

* Change local value declaration to var

* Remove unused fields

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

@@ -0,0 +1,86 @@
+/**
+ * The MIT License
+ * Copyright (c) 2014-2016 Ilkka Seppälä
+ * <p>
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * <p>
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * <p>
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+package com.iluwatar.doublebuffer;
+
+import org.apache.commons.lang3.tuple.Pair;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.util.List;
+
+/**
+ * Scene class. Render the output frame.
+ */
+public class Scene {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(Scene.class);
+
+  private Buffer[] frameBuffers;
+
+  private int current;
+
+  private int next;
+
+  /**
+   * Constructor of Scene.
+   */
+  public Scene() {
+    frameBuffers = new FrameBuffer[2];
+    frameBuffers[0] = new FrameBuffer();
+    frameBuffers[1] = new FrameBuffer();
+    current = 0;
+    next = 1;
+  }
+
+  /**
+   * Draw the next frame.
+   * @param coordinateList list of pixels of which the color should be black
+   */
+  public void draw(List<Pair<Integer, Integer>> coordinateList) {
+    LOGGER.info("Start drawing next frame");
+    LOGGER.info("Current buffer: " + current + " Next buffer: " + next);
+    frameBuffers[next].clearAll();
+    for (Pair<Integer, Integer> coordinate : coordinateList) {
+      var x = coordinate.getKey();
+      var y = coordinate.getValue();
+      frameBuffers[next].draw(x, y);
+    }
+    LOGGER.info("Swap current and next buffer");
+    swap();
+    LOGGER.info("Finish swapping");
+    LOGGER.info("Current buffer: " + current + " Next buffer: " + next);
+  }
+
+  public Buffer getBuffer() {
+    LOGGER.info("Get current buffer: " + current);
+    return frameBuffers[current];
+  }
+
+  private void swap() {
+    current = current ^ next;
+    next = current ^ next;
+    current = current ^ next;
+  }
+
+}