JAVA1．定义复数（Complex）类。要求：（1）复数有实部和虚部属性；（2）定义类的构造方法；（3）实现复数加减法并输出复数属性的值。（4）重载toString方法，用于对象属性值的输出。

下面是一个简单的Java实现，实现了复数类的定义、构造方法、复数加减法和toString方法的重载：

public class Complex {
    private double real; // 实部
    private double imag; // 虚部

    // 构造方法，初始化实部和虚部
    public Complex(double real, double imag) {
        this.real = real;
        this.imag = imag;
    }

    // 复数加法
    public Complex add(Complex other) {
        double realSum = this.real + other.real;
        double imagSum = this.imag + other.imag;
        return new Complex(realSum, imagSum);
    }

    // 复数减法
    public Complex subtract(Complex other) {
        double realDiff = this.real - other.real;
        double imagDiff = this.imag - other.imag;
        return new Complex(realDiff, imagDiff);
    }

    // 重载toString方法，用于对象属性值的输出
    public String toString() {
        if (imag >= 0) {
            return "(" + real + " + " + imag + "i)";
        } else {
            return "(" + real + " - " + (-imag) + "i)";
        }
    }
}

使用示例：

public class Test {
    public static void main(String[] args) {
        Complex a = new Complex(1, 2);
        Complex b = new Complex(2, -1);
        Complex c = a.add(b);
        Complex d = a.subtract(b);

        System.out.println("a = " + a);
        System.out.println("b = " + b);
        System.out.println("a + b = " + c);
        System.out.println("a - b = " + d);
    }
}

输出结果：

a = (1.0 + 2.0i)
b = (2.0 - 1.0i)
a + b = (3.0 + 1.0i)
a - b = (-1.0 + 3.0i)