Question

AtomicFile 在 android.support.v4.util 包下， 是一个与文件相关的工具类，其作用是保证文件读写的原子性。 即文件读写的时候全部成功才会更新文件，如果失败则不会影响文件内容。

看官方对其说明：

Static library support version of the framework's AtomicFile , a helper class for performing atomic operations on a file by creating a backup file until a write has successfully completed.

静态支持库版本的 AtomicFile，一个帮助类，用于通过创建备份文件对文件执行原子操作，直到写入成功完成。

Atomic file guarantees file integrity by ensuring that a file has been completely written and sync'd to disk before removing its backup. As long as the backup file exists, the original file is considered to be invalid (left over from a previous attempt to write the file).

原子文件通过确保文件在删除其备份之前已经完全写入并同步到磁盘，从而保证文件的完整性。只要备份文件存在，原始文件将被视为无效（会尝试写入备份文件中）。

Atomic file does not confer any file locking semantics. Do not use this class when the file may be accessed or modified concurrently by multiple threads or processes. The caller is responsible for ensuring appropriate mutual exclusion invariants whenever it accesses the file.

原子文件不提供任何文件锁定语义。当文件可能被多个线程或进程并发访问或修改时，不要使用此类。每当访问文件时，调用者都负责确保适当的互斥变量。