第二:Object的getClass()方法的释义是:返回此 Object 的运行时类。返回的 Class 对象是由所表示类的 static synchronized 方法锁定的对象。
/**
* Returns the runtime class of this {@code Object}. The returned
* {@code Class} object is the object that is locked by {@code
* static synchronized} methods of the represented class.
**/