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FileVisitor (Java SE 26 & JDK 26)

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Hide sidebar Show sidebar Type Parameters: T - the type of file/directory All Known Implementing Classes: SimpleFileVisitor

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.

Copy 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.

Copy 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; } });

Since: 1.7

Method Summary

All MethodsInstance MethodsAbstract Methods

Modifier and Type

Method

Description

FileVisitResult

postVisitDirectory(T dir, IOException exc)

Invoked for a directory after entries in the directory, and all of their descendants, have been visited.

FileVisitResult

preVisitDirectory(T dir, BasicFileAttributes attrs)

Invoked for a directory before entries in the directory are visited.

FileVisitResult

visitFile(T file, BasicFileAttributes attrs)

Invoked for a file in a directory.

FileVisitResult

visitFileFailed(T file, IOException exc)

Invoked for a file that could not be visited.

Method Details
- preVisitDirectory
  
  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.
  Parameters: dir - a reference to the directory attrs - the directory's basic attributes Returns: the visit result Throws: IOException - if an I/O error occurs
- visitFile
  
  FileVisitResult visitFile(T file, BasicFileAttributes attrs) throws IOException
  
  Invoked for a file in a directory.
  Parameters: file - a reference to the file attrs - the file's basic attributes Returns: the visit result Throws: IOException - if an I/O error occurs
- visitFileFailed
  
  FileVisitResult 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.
  Parameters: file - a reference to the file exc - the I/O exception that prevented the file from being visited Returns: the visit result Throws: IOException - if an I/O error occurs
- postVisitDirectory
  
  FileVisitResult 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).
  Parameters: dir - a reference to the directory exc - 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 Returns: the visit result Throws: IOException - if an I/O error occurs

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Interface FileVisitor<T>

Method Summary

Method Details

preVisitDirectory

visitFile

visitFileFailed

postVisitDirectory