错误提示：The method play() is undefined for the type Object

如何在测试类的主方法里正确调用内部类的void plany打印输出方法?

package com.imooc.exercise.polymorphism;

//测试类

public class Test {

  public static void main(String[] args) {

//完成成员内部类内部测试

  BallTest.Inner_m basketball=new BallTest().new Inner_m();

  basketball.play();

      BallTest one=new BallTest(); 

   //完成方法内部类测试

      one.info().play();

    //错误提示：The method play() is undefined for the type Object  

   }

}

​

package com.imooc.exercise.polymorphism;

//创建类BallTest

public class BallTest {  

  public Inner_m getInner_m() {

  return new Inner_m();

   }

// 创建成员内部类Inner_m

  class Inner_m{      

      public void play(){

          System.out.println("成员内部类:");

          System.out.println("打篮球");

          System.out.println("*********************");

     }

  }

    // 创建方法内部类

  public Object info() {

   class Inner_f implements Ball{

    public void play() {

    System.out.println("******************");

    System.out.println("方法内部类：");

    System.out.println("打乒乓球");  

   }   

   }

    return new Inner_f();

   }

// 定义一个方法void playBall(Ball ball)，调用play()方法

  public void playBall(Ball ball) {

      ball.play();

  }

}

package com.imooc.exercise.polymorphism;

public interface Ball {

        void play();      

}