renameTo,故名思义,是改名,如果指定了不同的目录,各个OS的表现形式是不一致的
/**
* Renames the file denoted by this abstract pathname.
*
* <p> Many aspects of the behavior of this method are inherently
* platform-dependent: The rename operation might not be able to move a
* file from one filesystem to another, it might not be atomic, and it
* might not succeed if a file with the destination abstract pathname
* already exists. The return value should always be checked to make sure
* that the rename operation was successful.
即使会移动吧,那个也是move而不是copy!