设计一个复数类，实现两个复数相加减

设计一个复数类（ComplexNumber），首先需要包含两个私有成员变量：实部（real）和虚部（imaginary）。为了实现复数的加法和减法操作，我们可以创建公共方法：

public class ComplexNumber {
    private double real;
    private double imaginary;

    // 构造函数
    public ComplexNumber(double real, double imaginary) {
        this.real = real;
        this.imaginary = imaginary;
    }

    // 实现复数相加
    public ComplexNumber add(ComplexNumber other) {
        double newReal = this.real + other.real;
        double newImaginary = this.imaginary + other.imaginary;
        return new ComplexNumber(newReal, newImaginary);
    }

    // 实现复数相减
    public ComplexNumber subtract(ComplexNumber other) {
        double newReal = this.real - other.real;
        double newImaginary = this.imaginary - other.imaginary;
        return new ComplexNumber(newReal, newImaginary);
    }

    // 返回字符串表示形式
    @Override
    public String toString() {
        return "ComplexNumber{" +
                "real=" + real +
                ", imaginary=" + imaginary +
                '}';
    }
}

在这个类中，我们通过`add()`和`subtract()`方法接受另一个复数作为参数，并计算出结果的新复数。每个方法内部处理了实部和虚部的加减运算。

你可以这样使用这个类：

public static void main(String[] args) {
    ComplexNumber num1 = new ComplexNumber(2, 3);
    ComplexNumber num2 = new ComplexNumber(4, -5);

    ComplexNumber sum = num1.add(num2);
    System.out.println("Sum: " + sum); // 输出：Sum: ComplexNumber{real=6, imaginary=-2}

    ComplexNumber difference = num1.subtract(num2);
    System.out.println("Difference: " + difference); // 输出：Difference: ComplexNumber{real=-2, imaginary=8}
}