提供对本地文件系统的访问功能.当试图对一个已经关闭的对象进行操作时，会抛出此异常。这是一个很关键的类，基本上文件读写都是有该类完成。可以从字面上去理解它的意思。这个类我也没用过，不知道它具体的功能。用于监听文件系统目录状态的变化，比如文件的删除、新增，存储卡的拔出和插入等。用于管理和跟踪文件系统的监听器，以及可以通过此类过去当前所有文件系统的根目录.文件打开模式异常，当试图写入以只读方式打开的文件时，会抛出该异常。 -Provides the local file system access. When one attempts to manipulate an object has been closed, we will throw this exception. This is a very critical group, largely to complete the class are all read and write files. You can literally try to understand what it means. I did not used to this class, do not know the specific function. The file system directory used to monitor changes in the status, such as file deletion, adding, memory cards, pull out, and insertion. The file system for managing and tracking the listener, as well as through these past all current file system root directory. File Open Mode Exception, when trying to write to read-only open file, it will throw the exception.