FileVisitor
public interface FileVisitor
| java.nio.file.FileVisitor<T> |
Known indirect subclasses | SimpleFileVisitor<T> | A simple visitor of files with default behavior to visit all files and to re-throw I/O errors. | |
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; } }); Summary
Public methods
postVisitDirectory
public abstract FileVisitResult postVisitDirectory (T dir, IOException exc)
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 |
preVisitDirectory
public abstract FileVisitResult preVisitDirectory (T dir, BasicFileAttributes attrs)
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 |
visitFile
public abstract FileVisitResult visitFile (T file, BasicFileAttributes attrs)
Invoked for a file in a directory.
| Parameters |
|---|
file | T: a reference to the file |
attrs | BasicFileAttributes: the file's basic attributes |
visitFileFailed
public abstract FileVisitResult visitFileFailed (T file, IOException exc)
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 |
