public boolean buyProps(Prop wantedProp)
    {
         if (this.propPackage.size() <= 10)
         {
            this.propPackage.add(wantedProp);
             return true;
         }
        else
         {
             System.out.println("您的包裹满了，最多只能装10个道具。");
         }
        return false;
    }