用java编写编写复数类，并在主类中完成复数的四则运算并输出结果！

好的，以下是用Java编写的复数类及其四则运算的代码：

public class Complex {
    private double real;
    private double imag;

    public Complex(double real, double imag) {
        this.real = real;
        this.imag = imag;
    }

    public Complex add(Complex other) {
        return new Complex(this.real + other.real, this.imag + other.imag);
    }

    public Complex subtract(Complex other) {
        return new Complex(this.real - other.real, this.imag - other.imag);
    }

    public Complex multiply(Complex other) {
        double real = this.real * other.real - this.imag * other.imag;
        double imag = this.real * other.imag + this.imag * other.real;
        return new Complex(real, imag);
    }

    public Complex divide(Complex other) {
        double denominator = other.real * other.real + other.imag * other.imag;
        double real = (this.real * other.real + this.imag * other.imag) / denominator;
        double imag = (this.imag * other.real - this.real * other.imag) / denominator;
        return new Complex(real, imag);
    }

    public String toString() {
        if (imag >= 0) {
            return String.format("%.2f+%.2fi", real, imag);
        } else {
            return String.format("%.2f-%.2fi", real, -imag);
        }
    }
}

以下是主类中的代码：

public class Main {
    public static void main(String[] args) {
        Complex a = new Complex(1, 2);
        Complex b = new Complex(3, 4);

        System.out.println("a = " + a);
        System.out.println("b = " + b);
        System.out.println("a + b = " + a.add(b));
        System.out.println("a - b = " + a.subtract(b));
        System.out.println("a * b = " + a.multiply(b));
        System.out.println("a / b = " + a.divide(b));
    }
}

输出结果为：

a = 1.00+2.00i
b = 3.00+4.00i
a + b = 4.00+6.00i
a - b = -2.00-2.00i
a * b = -5.00+10.00i
a / b = 0.44+0.08i

希望这个回答能够帮到你！