Cannot refer to a nonfinal variable music inside an inner class defined in a different method

Change modifier of 'music' to final

http://stackoverflow.com/questions/1299837/cannot-refer-to-a-non-final-variable-inside-an-inner-class-defined-in-a-differen

最近在写程序的时候一直出现这个提示,一直没有时间来查询原因.不解,先把标题留在这儿,有时间了来查看

还有一个是实例化后的对象在赋为  return null时没有为null