写一个Rectangle类，描述一个矩形。 具备以下域： 四个顶点的坐标leftTop，rightTop，leftFloor，rightFloor，以Point对象表示； 图形的周长； 图形的面积。 构造器： 无参构造器 Rectangle（），生成一个四个顶点均为（0.0，0.0）的矩形； Rectangle（double x1, double y1, double x2, double y2），其中（x1, y1）是一个顶点，其中（x2, y2）是对角线上另一个顶点； Rectangle（Point p1，Point p2），p1、p2是对角线上的两个顶点。 设计如下方法： Point getLeftTop（）； Point getLeftFloor（）； Point getRightTop（）； Point getRightFloor（）； 返回周长； 返回面积。 写一个测试类，测试Rectangle类。

Rectangle类的代码如下：

public class Rectangle {
    private Point leftTop;
    private Point rightTop;
    private Point leftFloor;
    private Point rightFloor;

    public Rectangle() {
        this.leftTop = new Point(0.0, 0.0);
        this.rightTop = new Point(0.0, 0.0);
        this.leftFloor = new Point(0.0, 0.0);
        this.rightFloor = new Point(0.0, 0.0);
    }

    public Rectangle(double x1, double y1, double x2, double y2) {
        this.leftTop = new Point(x1, y1);
        this.rightTop = new Point(x2, y1);
        this.leftFloor = new Point(x1, y2);
        this.rightFloor = new Point(x2, y2);
    }

    public Rectangle(Point p1, Point p2) {
        this.leftTop = new Point(Math.min(p1.getX(), p2.getX()), Math.min(p1.getY(), p2.getY()));
        this.rightTop = new Point(Math.max(p1.getX(), p2.getX()), Math.min(p1.getY(), p2.getY()));
        this.leftFloor = new Point(Math.min(p1.getX(), p2.getX()), Math.max(p1.getY(), p2.getY()));
        this.rightFloor = new Point(Math.max(p1.getX(), p2.getX()), Math.max(p1.getY(), p2.getY()));
    }

    public Point getLeftTop() {
        return leftTop;
    }

    public Point getLeftFloor() {
        return leftFloor;
    }

    public Point getRightTop() {
        return rightTop;
    }

    public Point getRightFloor() {
        return rightFloor;
    }

    public double getPerimeter() {
        return 2 * (Math.abs(leftTop.getX() - rightTop.getX()) + Math.abs(leftTop.getY() - leftFloor.getY()));
    }

    public double getArea() {
        return Math.abs(leftTop.getX() - rightTop.getX()) * Math.abs(leftTop.getY() - leftFloor.getY());
    }
}

测试类的代码如下：

public class RectangleTest {
    public static void main(String[] args) {
        Rectangle r1 = new Rectangle();
        Rectangle r2 = new Rectangle(1.0, 1.0, 3.0, 4.0);
        Rectangle r3 = new Rectangle(new Point(2.0, 3.0), new Point(5.0, 6.0));

        System.out.println("r1 perimeter: " + r1.getPerimeter());
        System.out.println("r1 area: " + r1.getArea());
        System.out.println("r2 perimeter: " + r2.getPerimeter());
        System.out.println("r2 area: " + r2.getArea());
        System.out.println("r3 perimeter: " + r3.getPerimeter());
        System.out.println("r3 area: " + r3.getArea());
    }
}

输出结果如下：

r1 perimeter: 0.0
r1 area: 0.0
r2 perimeter: 10.0
r2 area: 6.0
r3 perimeter: 12.0
r3 area: 9.0