说明：  在许多面向对象程序设计语言中，属性(property)是指对象的特征和状态，具体地说就是指对象的数据成员。程序员可以指定数据成员能否被外界直接访问，如果数据成员被指定为public的，外界就可以用“对象名.公有数据成员名”访问该成员。
(In many object-oriented programming language, attributes (property) is refers to the object s characteristics and state, specifically refers to the object data member programmers can be specified data members can be direct access to the outside world, if the data members being designated as public, the outside world can use object name. Public data member name visit to the members )