Java：关于复数编程的问题+scanner和构造方法的结合

1.问下这个关于复数的题哪里有问题？为什么运行不出来？
2.Java怎么通过scanner输入的参数个数来调用对应参数个数的构造方法的？

package step1;
import java.util.Scanner;

class Complex {
    //定义属性
    private double real;
    private double imagin;
    //定义构造方法
    public Complex(){
    }
    public Complex(double real){
        this.real = real;
    }
    public Complex(double real, double imagin){
        this.real = real;
        this.imagin = imagin;
    }
    //定义方法
    public Complex Plus(Complex n3){
        Complex n4 = new Complex();
        n4.real = this.real + n3.real;
        n4.imagin = this.imagin + n3.imagin;
        return n4;
    }
    public Complex Sub(Complex n3){
        Complex n4 = new Complex();
        n4.real = this.real - n3.real;
        n4.imagin = this.imagin - n3.imagin;
        return n4;
    }
    //覆盖
    @Override
    public String toString(){
        if(imagin>=0){
            return(real + "+"+ imagin+ "i");
        }else{
            return(real + "-"+ imagin +"i");
        }
    }
}

    
class ComplexTest{
    public static void main(String[] args){
    Complex n0 = new Complex();
    Scanner sc = new Scanner(System.in);
    double real1 = sc.nextDouble();
    double imagin1 = sc.nextDouble();
    Complex n1 = new Complex(real1,imagin1);
    //输出结果
    System.out.println(n0.Plus(n1));
    System.out.println(n0.Sub(n1));
    System.out.print(n0 + " "+ n1);
    }
}

使用了Scanner ，你得输入参数之后才能运行呀， 调用对应的构造参数，跟你调用参数的个数有关呀，比如有以下两个构造方法
那你使用 Scanner sc = new Scanner(System.in); 肯定对应调用一个参数的方法呗
public Scanner(InputStream source) {
this(new InputStreamReader(source), WHITESPACE_PATTERN);
}
public Scanner(InputStream source, String charsetName) {
this(makeReadable(Objects.requireNonNull(source, "source"), toCharset(charsetName)),
WHITESPACE_PATTERN);
}

额...您能帮我改下代码吗？
我还是不是很懂....