Some Unix operating systems, including Linux, provide BSD-style (flock
) locks, so it might be thought that Java FileLock
could be implemented using BSD-style locks rather than POSIX locks. But that is not possible, because BSD-style locks are whole-file locks rather than record locks, and FileLock
is a record lock: each lock is for a range of bytes in a file. Thus there is no real choice on a Unix system, and assuming that the implementation of FileLock
uses POSIX fcntl
locks is a safe assumption on a Unix operating system.
The resulting FileLock
locks might or might not interact with BSD-style locks. BSD-style locks can be implemented using POSIX locks (this was the case for Linux before version 2.0), or the operating system might have the two styles of locking interact (this is the case for FreeBSD). But in general that can not be guaranteed, and BSD-style locks and Java locks might be effectively invisible to each other (this is the case for any version of Linux you are likely to encounter).