【牛客带你学编程Java方向】项目练习第4期（参考答案）

/** 
* @file Programme2.java 
* @CopyRight (C) http://www.wogeeker.cn 
* @brief * @author louxiujun 
* @email louxj424@126.com 
* @date 2017/11/16 
*/ public class Programme2 { public static void main(String[] args){
        Square square=new Square(); double square_area=square.area(2);
        System.out.println(square_area);
        Circle circle=new Circle(); double circle_area=circle.area(3);
        System.out.println(circle_area);
    }
} interface Shape{ double area(double len);
} class Square implements Shape{ public double area(double len) { return len*len;
    }
} class Circle implements Shape { public double area(double len) { return len*len*Math.PI;
    }
}