面向对象案例

1.求矩形、正方形和圆形的面积与周长

package randi;

import static java.lang.Math.PI;

public class ShapeDemo {

    public static void main(String[] args) {

        Shape[] shas = new Shape[] { new Circle(10), new Rect(5, 6), new Squr(10) };
        Shape sha = new Shape();

        for (int i = 0; i < shas.length; i++) {
            sha.print(shas[i]);
        }

//        Circle s1 = new Circle(10);
//        Rect s2 = new Rect(5, 6);
//        Squr s3 = new Squr(10);
//
//        sha.print(s1);
//        sha.print(s2);
//        sha.print(s3);
    }

}

class Shape {

    public void print(Shape sha) {
        System.out.println(sha.getName() + "面积: " + sha.getArea());
        System.out.println(sha.getName() + "周长: " + sha.getGirth());
        System.out.println("---------------");
    }

    public double getArea() {
        return -1;
    }

    public double getGirth() {
        return -1;
    }

    public String getName() {
        return null;
    }
}

class Circle extends Shape {
    private double radius;

    public Circle() {}

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

    }

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

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

    public String getName() {
        return "Cir";
    }

}

class Rect extends Shape {
    private double length;
    private double width;

    public Rect() {}

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

    }

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

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

    public String getName() {
        return "Rect";
    }

}

class Squr extends Rect {

    public Squr() {}

    public Squr(double length) {
        super(length, length);

    }

    public String getName() {
        return "Squr";
    }

}

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