Your browser does not seem to support JavaScript. As a result, your viewing experience will be diminished, and you may not be able to execute some actions.
Please download a browser that supports JavaScript, or enable it if it's disabled (i.e. NoScript).
看一些边界条件,都会定义多个构造函数,每个构造函数的输入量不同,为什么需要多个构造函数呢?