java利用接口计算圆的面积

接口代码

package Area;

public interface Area {

double area();

}

接口子类代码

package Area;

public class areaimpl implements Area{

private Double r;

public Double getR() {

return r;

}

public void setR(Double r) {

this.r = r;

}

@Override

public double area() {

// TODO Auto-generated method stub

return (3.14 * getR() * getR());

}

}测试类代码
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package Area;

import java.util.Scanner;

public class Areademo {

public static void main(String[] args) {

// TODO Auto-generated method stub

Scanner sc = new Scanner(System.in);

System.out.println("--------计算圆形的面积-------");

System.out.print("请输入圆形的半径：");

areaimpl r = new areaimpl();

Double r1 = sc.nextDouble();

r.setR(r1);

System.out.println("半径为"+r.getR()+"的圆面积为"+r.area());

}

}