Java基础 接口实现 设计一个形状类(接口)Shape,方法:求周长和求面积

题目：
设计一个形状类(接口)Shape,方法:求周长和求面积形状类(接口)的子类(实现类);:Rect(矩形),Circle(圆形)Rect类的子类:Square(正方形)不同的子类会有不同的计算周长和面积的方法。
创建三个不同的形状对象,放在Shape类型的数组里,分别打印出每个对象的周长和面积。

形状接口

public interface Shape {
   
	// 求面积方法
	double getArea();

	// 求周长方法
	double getPerimeter();
}

圆形类

public class Circle implements Shape {
   
	private final double PI = 3.14;  //圆周率
	private double r;   //半径

	public double getR() {
   
		return r;
	}
	public void setR(double r) {
   
		this.r = r;
	}
	public Circle(double r) {
   
		this.r = r;
	}

	@Override
	public double getArea() {
   
		// TODO Auto-generated method stub
		return PI * r * r;
	}

	@Override
	public double getPerimeter() {
   
		// TODO Auto-generated method stub
		return PI * r * 2;
	}
}

矩形类

public class Rect implements Shape {
   
	private double width; // 宽
	private double height; // 高

	public double getWidth() {
   
		return width;
	}
	public void setWidth(double width) {
   
		this.width = width;
	}
	public double getHeight() {
   
		return height;
	}
	public void setHeight(double height) {
   
		this.height = height;
	}
	
	// 一个参数构造，给子类正方形用
	public Rect(double width) {
   
		this.width = width;
	}

	//两个参数的构造，自己用
	public Rect(double width, double height) {
   
		this.height = height;
		this.width = width;
	}

	@Override
	public double getArea() {
   
		// TODO Auto-generated method stub
		return width * height;
	}

	@Override
	public double getPerimeter() {
   
		// TODO Auto-generated method stub
		return 2 * (width + height);
	}
}

正方形，继承矩形

public class Square extends Rect {
   
	public Square(double width) {
   
		super(width);
	}

	@Override
	public double getArea() {
   
		// TODO Auto-generated method stub
		return getWidth() * getWidth();
	}

	@Override
	public double getPerimeter() {
   
		// TODO Auto-generated method stub
		return 4 * getWidth();
	}
}

测试类

public class Test {
   

	public static void main(String[] args) {
   

		Shape[] shape = new Shape[3];
		shape[0] = new Circle(3);

		System.out.println("========圆形周长和面积========");
		System.out.println(String.format("%.2f", shape[0].getArea()));
		System.out.println(shape[0].getPerimeter());

		shape[1] = new Rect(5, 8);
		System.out.println("========矩形周长和面积========");
		System.out.println(shape[1].getArea());
		System.out.println(shape[1].getPerimeter());

		shape[2] = new Square(5);
		System.out.println("========正方形周长和面积========");
		System.out.println(shape[2].getArea());
		System.out.println(shape[2].getPerimeter());
	}
}

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