Game Loop Pattern (#1083)

* Add game loop module * Add game loop module * Fix merge issue * Implement game loop module * Implement game loop module * Implement time based game loop * implement VariableStepGameLoop * Implement FixedStepGameLoop * Add UT * Add Unit tests * Fix checkstyle issues * Add README.md * Fix code review issues * Fix code review issues * update README.md
2026-05-14 12:58:37 +00:00 · 2019-11-16 20:40:23 +08:00
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+/*
+ * The MIT License
+ * Copyright © 2014-2019 Ilkka Seppälä
+ *
+ * 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:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * 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.gameloop;
+
+import java.util.Random;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Abstract class for GameLoop implementation class.
+ */
+public abstract class GameLoop {
+
+  protected final Logger logger = LoggerFactory.getLogger(this.getClass());
+
+  protected volatile GameStatus status;
+
+  protected GameController controller;
+
+  private Thread gameThread;
+
+  /**
+   * Initialize game status to be stopped.
+   */
+  public GameLoop() {
+    controller = new GameController();
+    status = GameStatus.STOPPED;
+  }
+
+  /**
+   * Run game loop.
+   */
+  public void run() {
+    status = GameStatus.RUNNING;
+    gameThread = new Thread(() -> processGameLoop());
+    gameThread.start();
+  }
+
+  /**
+   * Stop game loop.
+   */
+  public void stop() {
+    status = GameStatus.STOPPED;
+  }
+
+  /**
+   * Check if game is running or not.
+   *
+   * @return {@code true} if the game is running.
+   */
+  public boolean isGameRunning() {
+    return status == GameStatus.RUNNING ? true : false;
+  }
+
+  /**
+   * Handle any user input that has happened since the last call. In order to
+   * simulate the situation in real-life game, here we add a random time lag.
+   * The time lag ranges from 50 ms to 250 ms.
+   */
+  protected void processInput() {
+    try {
+      int lag = new Random().nextInt(200) + 50;
+      Thread.sleep(lag);
+    } catch (InterruptedException e) {
+      logger.error(e.getMessage());
+    }
+  }
+
+  /**
+   * Render game frames to screen. Here we print bullet position to simulate
+   * this process.
+   */
+  protected void render() {
+    var position = controller.getBulletPosition();
+    logger.info("Current bullet position: " + position);
+  }
+
+  /**
+   * execute game loop logic.
+   */
+  protected abstract void processGameLoop();
+
+}