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，并定义它与复数、实数相加和相减及复数间乘、除的方法-Definition of a complex class constructor assigned to a complex object, real and imaginary parts of the private property of the class must have a method to access and modif