The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
You have a Path
instance representing a file or directory, but does that file exist on the file system? Is it readable? Writable? Executable?
The methods in the Path
class are syntactic, meaning that they operate on the Path
instance. But eventually you must access the file system to verify that a particular Path
exists, or does not exist. You can do so with the
exists(Path, LinkOption...)
and the
notExists(Path, LinkOption...)
methods. Note that !Files.exists(path)
is not equivalent to Files.notExists(path)
. When you are testing a file's existence, three results are possible:
If both exists
and notExists
return false
, the existence of the file cannot be verified.
To verify that the program can access a file as needed, you can use the
isReadable(Path)
,
isWritable(Path)
, and
isExecutable(Path)
methods.
The following code snippet verifies that a particular file exists and that the program has the ability to execute the file.
Path file = ...; boolean isRegularExecutableFile = Files.isRegularFile(file) & Files.isReadable(file) & Files.isExecutable(file);
TOCTTOU
(pronounced TOCK-too).
When you have a file system that uses symbolic links, it is possible to have two different paths that locate the same file. The
isSameFile(Path, Path)
method compares two paths to determine if they locate the same file on the file system. For example:
Path p1 = ...; Path p2 = ...; if (Files.isSameFile(p1, p2)) { // Logic when the paths locate the same file }