interface Sport{ void play();}class Display{ public void show(){ System.out.println("运动器材信息："); } }class Ball extends Display Sport{ String color; double price; public Ball(String color,double price) { this.color=color; this.setPrice(price); } public double getPrice() { return price; } public void setPrice(double price) { if(price<0){ this.price = price; }else System.out.println("错误！"); }@Override public void play() { System.out.println("用脚踢着玩！"); }