任务2：声明复数类Complex，成员变量包括实部和虚部，类型均为double。要求该类具有 (1)实现多个构造方法（如无参构造方法、1个参数构造方法，2个参数构造方法，字符串参数的构造方法）。 (2)使用getter和setter完成属性的访问和修改 (3)成员方法包括实现复数加法add、减法minus、乘法multiply，计算模长length (4)重写equals()方法，只有当两个复数实部和虚部都相等时，才返回真 (5)重写toString()，输出复数信息 (6)在main方法中，使用实际数据测试成员方法

好的，我已经理解了你的要求。以下是实现复数类Complex的代码：

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

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

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

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

    public Complex(String complex) {
        String[] parts = complex.split("\\+");
        this.real = Double.parseDouble(parts[0]);
        this.imaginary = Double.parseDouble(parts[1].replace("i", ""));
    }

    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;
    }

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

    public Complex minus(Complex other) {
        return new Complex(this.real - other.real, this.imaginary - other.imaginary);
    }

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

    public double length() {
        return Math.sqrt(this.real * this.real + this.imaginary * this.imaginary);
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Complex) {
            Complex other = (Complex) obj;
            return this.real == other.real && this.imaginary == other.imaginary;
        }
        return false;
    }

    @Override
    public String toString() {
        if (this.imaginary == 0) {
            return Double.toString(this.real);
        } else if (this.real == 0) {
            return Double.toString(this.imaginary) + "i";
        } else {
            return Double.toString(this.real) + "+" + Double.toString(this.imaginary) + "i";
        }
    }

    public static void main(String[] args) {
        Complex c1 = new Complex(1, 2);
        Complex c2 = new Complex(3, -4);
        Complex c3 = new Complex("5+6i");

        System.out.println(c1.add(c2));
        System.out.println(c1.minus(c2));
        System.out.println(c1.multiply(c2));
        System.out.println(c1.length());
        System.out.println(c1.equals(new Complex(1, 2)));
        System.out.println(c3);
    }
}

在上面的代码中，我们首先定义了一个叫做Complex的类。该类有两个成员变量，分别是实部和虚部，类型均为double。然后我们实现了多个构造方法，包括无参构造方法、1个参数构造方法，2个参数构造方法，以及字符串参数的构造方法。

接下来，我们使用getter和setter完成属性的访问和修改。在此基础上，我们实现了复数加法add、减法minus、乘法multiply，计算模长length等成员方法。同时，我们还重写了equals()方法和toString()方法，分别用于比较两个复数是否相等，以及输出复数信息。

最后，在main方法中，我们使用实际数据测试了成员方法的正确性。我相信这个复数类可以满足你的需求。