类中包括四种成员：成员变量、getter和setter、构造方法及方 法。 对成员变量进行保护，对传入数据进行检验，如数据不在 正确范围内，抛出异常信息；构造方法分无参、有参两种 设计复数类Complex，计算两个复数之和、差，同时以 a＋bi 的字符串形式显示。使用复数类Complex，验证两个复数 1＋2i 和3＋4i 相加产生一个新的复数 4＋6i ，相减产生一个新的复数 2 2i。

下面是一个复数类Complex的示例代码，包括成员变量、getter和setter、构造方法及方法：

public class Complex {
    private double real; // 复数的实部
    private double imaginary; // 复数的虚部

    public Complex() {
        this.real = 0;
        this.imaginary = 0;
    }

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

    public double getReal() {
        return real;
    }

    public void setReal(double real) {
        this.real = real;
    }

    public double getImaginary() {
        return imaginary;
    }

    public void setImaginary(double imaginary) {
        this.imaginary = imaginary;
    }

    // 计算两个复数之和
    public Complex add(Complex other) {
        double sumReal = this.real + other.real;
        double sumImaginary = this.imaginary + other.imaginary;
        return new Complex(sumReal, sumImaginary);
    }

    // 计算两个复数之差
    public Complex subtract(Complex other) {
        double diffReal = this.real - other.real;
        double diffImaginary = this.imaginary - other.imaginary;
        return new Complex(diffReal, diffImaginary);
    }

    // 以 a＋bi 的字符串形式显示复数
    public String toString() {
        String sign = (this.imaginary >= 0) ? "+" : "-";
        return this.real + sign + Math.abs(this.imaginary) + "i";
    }
}

使用方法如下：

Complex c1 = new Complex(1, 2);
Complex c2 = new Complex(3, 4);
Complex sum = c1.add(c2);
Complex diff = c1.subtract(c2);
System.out.println("Sum: " + sum.toString()); // 输出 "Sum: 4+6i"
System.out.println("Difference: " + diff.toString()); // 输出 "Difference: -2-2i"