定义一个复数类，可以通过构造函数给复数对象赋值，实部和虚部是该类的私有属性，

必须有获取和修改属性的方法，并定义复数间加减乘除的方法。

把文件夹复制到运行目录下，用eclipse打开-Define a Plural class, you can assign an object constructor function to the plural, real and imaginary parts are of such private property,

Must have access and modify the properties of the method, and the definition of plural multiplication and division between the addition and subtraction method.