java题，用有参和无参构造并赋值，r1和r2分别调用当中的一个方法并得出结果

Question

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看图片，详细要求全在里面了 主要是java用用有参和无参构造并赋值，r1和r2分别调用当中的一个方法并得出结果

Answer 1

package ch4;

public class Rect {
    private double length;
    private double width;
    private double area;

    public Rect() {
        this.length = 0;
        this.width = 0;
        this.area = 0;
    }

    public Rect(double length, double width) {
        this.length = length;
        this.width = width;
        this.area = length * width;
    }

    public double getArea() {
        return this.area;
    }

    public static void main(String[] args) {
        Rect r1 = new Rect();
        r1.length = 10;
        r1.width = 5;
        r1.area = r1.length * r1.width;
        System.out.println("r1的面积为：" + r1.getArea());

        Rect r2 = new Rect(20, 8);
        System.out.println("r2的面积为：" + r2.getArea());
    }
}

试一下行不行