FileVisitor
interface FileVisitor<T : Any!>
Known Direct Subclasses
SimpleFileVisitor |
A simple visitor of files with default behavior to visit all files and to re-throw I/O errors.
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A visitor of files. An implementation of this interface is provided to the java.nio.file.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;
}
});
Summary
Public methods |
abstract FileVisitResult! |
Invoked for a directory after entries in the directory, and all of their descendants, have been visited.
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abstract FileVisitResult! |
Invoked for a directory before entries in the directory are visited.
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abstract FileVisitResult! |
Invoked for a file in a directory.
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abstract FileVisitResult! |
Invoked for a file that could not be visited.
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Public methods
postVisitDirectory
abstract fun postVisitDirectory(
dir: T,
exc: IOException!
): FileVisitResult!
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).
Parameters |
dir |
T: a reference to the directory |
exc |
IOException!: 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 prematurely |
Exceptions |
java.io.IOException |
if an I/O error occurs |
preVisitDirectory
abstract fun preVisitDirectory(
dir: T,
attrs: BasicFileAttributes!
): FileVisitResult!
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.
Parameters |
dir |
T: a reference to the directory |
attrs |
BasicFileAttributes!: the directory's basic attributes |
Exceptions |
java.io.IOException |
if an I/O error occurs |
visitFile
abstract fun visitFile(
file: T,
attrs: BasicFileAttributes!
): FileVisitResult!
Invoked for a file in a directory.
Parameters |
file |
T: a reference to the file |
attrs |
BasicFileAttributes!: the file's basic attributes |
Exceptions |
java.io.IOException |
if an I/O error occurs |
visitFileFailed
abstract fun visitFileFailed(
file: T,
exc: IOException!
): FileVisitResult!
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.
Parameters |
file |
T: a reference to the file |
exc |
IOException!: the I/O exception that prevented the file from being visited |
Exceptions |
java.io.IOException |
if an I/O error occurs |