code: private static Engine parseEngine(String userAgentString) {
  		for (Engine engine : Engine.engines) {
  			if (engine.isMatch(userAgentString)) {
  				return engine;
  			}
  		}
  		return Engine.Unknown;
  	}
docs: 解析引擎类型
  
  @param userAgentString User-Agent字符串
  @return 引擎类型