code: public synchronized static void setMainEngine(Engine engine) {
  		if (engine == null) {
  			throw new IllegalArgumentException("Engine can not be null");
  		}
  		engine.name = Engine.MAIN_ENGINE_NAME;
  		engineMap.put(Engine.MAIN_ENGINE_NAME, engine);
  		Engine.MAIN_ENGINE = engine;
  	}
docs: Set main engine