判断下列程序是否存在问题? 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()); } }