Java利用继承和多态来求矩形、正方形和圆形的面积与周长

@Java

大家好，我是Ziph！

import static java.lang.Math.PI;

/**
 * @Author Ziph
 * @date 2020/2/20
 * @Email [email protected]
 */
public class Inherit {
    public static void main(String[] args) {
        Circle circle = new Circle(10);
        Rect rect = new Rect(10, 29);
        Square square = new Square(5);
        System.out.println("圆形的面积为：" + circle.area());
        System.out.println("圆形的周长为：" + circle.girth());
        System.out.println("矩形的面积为：" + rect.area());
        System.out.println("矩形的周长为：" + rect.girth());
        System.out.println("正方形的面积为：" + square.area());
        System.out.println("正方形的周长为：" + square.girth());
        System.out.println("下面用print方法打印的优点是：");
        System.out.println("避免代码的重复，降低耦合性!");
        //避免代码的重复，降低耦合性
        Inherit inherit = new Inherit();
        inherit.print(new Circle(10));
        inherit.print(new Rect(10,20));
        inherit.print(new Square(5));
    }

    public void print(Shape shape) {
        System.out.println(shape.area());
        System.out.println(shape.girth());
    }
}

class Shape {//形状

    public double area() {
        //面积
        return 0;
    }

    public double girth() {
        //周长
        return 0;
    }
}

class Circle extends Shape {//圆形
    private double radius;//半径

    public Circle(double radius) {
        this.radius = radius;
    }

    public double area() {
        return PI * radius * radius;
    }

    public double girth() {
        return 2 * PI * radius;
    }
}

class Rect extends Shape {//矩形
    private double length;//长
    private double width;//宽

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

    public double area() {
        return length * width;
    }

    public double girth() {
        return 2 * (length + width);
    }
}

class Square extends Shape {//正方形
    private double length;

    public Square(double length) {
        this.length = length;
    }

    public double area() {
        return length * length;
    }

    public double girth() {
        return 4 * length;
    }
}

执行结果：