interface Playable
{
        void play();
}
interface Bounceable
{
        void play();
}
interface Rollable extends Playable, Bounceable
{
        Ball ball = new Ball("PingPang");
}
class Ball implements Rollable
{
        private String name;
        public String getName()
{
            return name;
        }
        public Ball(String name)
{this.name = name;        
        }
       public void play()
{
            ball = new Ball("Football");
            System.out.println(ball.getName());
        }
}

我觉得ball = new Ball("Football");应该改成Ball ball = new Ball("Football");吧