public interface FileVisitor<T>
A visitor of files. An implementation of this interface is provided to the Files.walkFileTree
methods to visit each file in a file tree.
Usage Examples: Suppose we want to delete a file tree. In that case, each directory should be deleted after the entries in the directory are deleted.
Path start = ... Files.walkFileTree(start, new SimpleFileVisitor<Path>() { @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException { Files.delete(file); return FileVisitResult.CONTINUE; } @Override public FileVisitResult postVisitDirectory(Path dir, IOException e) throws IOException { if (e == null) { Files.delete(dir); return FileVisitResult.CONTINUE; } else { // directory iteration failed throw e; } } });
Furthermore, suppose we want to copy a file tree to a target location. In that case, symbolic links should be followed and the target directory should be created before the entries in the directory are copied.
final Path source = ... final Path target = ... Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE, new SimpleFileVisitor<Path>() { @Override public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException { Path targetdir = target.resolve(source.relativize(dir)); try { Files.copy(dir, targetdir); } catch (FileAlreadyExistsException e) { if (!Files.isDirectory(targetdir)) throw e; } return CONTINUE; } @Override public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException { Files.copy(file, target.resolve(source.relativize(file))); return CONTINUE; } });
FileVisitResult preVisitDirectory(T dir, BasicFileAttributes attrs) throws IOException
Invoked for a directory before entries in the directory are visited.
If this method returns CONTINUE
, then entries in the directory are visited. If this method returns SKIP_SUBTREE
or SKIP_SIBLINGS
then entries in the directory (and any descendants) will not be visited.
dir
- a reference to the directoryattrs
- the directory's basic attributesIOException
- if an I/O error occursFileVisitResult visitFile(T file, BasicFileAttributes attrs) throws IOException
Invoked for a file in a directory.
file
- a reference to the fileattrs
- the file's basic attributesIOException
- if an I/O error occursFileVisitResult visitFileFailed(T file, IOException exc) throws IOException
Invoked for a file that could not be visited. This method is invoked if the file's attributes could not be read, the file is a directory that could not be opened, and other reasons.
file
- a reference to the fileexc
- the I/O exception that prevented the file from being visitedIOException
- if an I/O error occursFileVisitResult postVisitDirectory(T dir, IOException exc) throws IOException
Invoked for a directory after entries in the directory, and all of their descendants, have been visited. This method is also invoked when iteration of the directory completes prematurely (by a visitFile
method returning SKIP_SIBLINGS
, or an I/O error when iterating over the directory).
dir
- a reference to the directoryexc
- null
if the iteration of the directory completes without an error; otherwise the I/O exception that caused the iteration of the directory to complete prematurelyIOException
- if an I/O error occurs
© 1993–2017, Oracle and/or its affiliates. All rights reserved.
Documentation extracted from Debian's OpenJDK Development Kit package.
Licensed under the GNU General Public License, version 2, with the Classpath Exception.
Various third party code in OpenJDK is licensed under different licenses (see Debian package).
Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.