关于复数的运算，求大神帮忙看看

Question

编写一个复数类，可以进行复数加法和减法运算。编写一个包含main方法的类（应用程序）测试该复数类。要求该复数类至少包含一个无参的构造方法和一个带参的构造方法；数据成员包括复数的实部和虚部，为double类型；包括两个方法，分别实现复数的加法和减法运算。代码import java.util.Scanner;public class ComplexNum { double RealNum; double ImagNum; public ComplexNum() { Scanner input=new Scanner(System.in); RealNum=input.nextDouble(); ImagNum=input.nextDouble(); //ComplexNum(RealNum,ImagNum); } public ComplexNum(double RealNum,double ImagNum) { this.RealNum=RealNum; this.ImagNum=ImagNum;    } public ComplexNum add(ComplexNum b) { double RealNum1=this.RealNum;     double ImagNum1=this.ImagNum;     double LastReal=RealNum+RealNum1;     double LastImag=ImagNum+ImagNum1;     ComplexNum result=new ComplexNum(LastReal,LastImag);     return result; } public ComplexNum mul(ComplexNum b) { double RealNum1=this.RealNum;     double ImagNum1=this.ImagNum;     double LastReal=RealNum-RealNum1;     double LastImag=ImagNum-ImagNum1;     ComplexNum result=new ComplexNum(LastReal,LastImag);     return result; } public void printf() { if(ImagNum>0) { System.out.println(ImagNum+"+"+"j"+RealNum); } else if(ImagNum<0) { System.out.println(ImagNum+"-"+"j"+RealNum); } else { System.out.println(RealNum); } } public static void main(String[] args) { System.out.println("请输入第一个复数的实部和虚部"); ComplexNum a=new ComplexNum(); System.out.println("请输入第二个复数的实部和虚部"); ComplexNum b=new ComplexNum();         ComplexNum add=a.add(b); ComplexNum mul=a.mul(b); add.printf(); mul.printf(); }}

Answer 1

代码怎么了？什么问题？