public class Demo1 {

    public static void main(String[] args) {

        Circle cir = new Circle();

        Rectangle rec = new Rectangle();

        cir.setR(4);

        rec.setLength(3);

        rec.setWidth(2);

        System.out.println("面积为:"+cir.area()+"\t周长为"+cir.perimeter());

        System.out.println("面积为:"+rec.area()+"\t周长为"+rec.perimeter());

    }

}

//定义接口

interface IShape1{

    public abstract double area();

}

interface IShape2{

    public abstract double perimeter();

}

//定义类

class Circle implements IShape1,IShape2{

    static final double pl=3.14;

    double r;

    public double getR() {

        return r;

    }

    public void setR(double r) {

        this.r = r;

    }

    public double area() {

        return pl*r*r;

    }

    public double perimeter(){

        return 2*pl*r;

    }

}

class Rectangle implements IShape1,IShape2{

    double length;

    double width;

    public double getLength() {

        return length;

    }

    public void setLength(double length) {

        this.length = length;

    }

    public double getWidth() {

        return width;

    }

    public void setWidth(double width) {

        this.width = width;

    }

    public double area() {

        return width*length;

    }

    public double perimeter(){

        return 2*(width+length);

    }

}