Spec-Zone .ru спецификации, руководства, описания, API

Please note that the specifications and other information contained herein are not final and are subject to change. The information is being made available to you solely for purpose of evaluation.

java.nio.file
Interface FileVisitor<T>

All Known Implementing Classes:

SimpleFileVisitor

public interface FileVisitor<T>

A visitor of files. An implementation of this interface is provided to the walkFileTree utility method to visit each file in a 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
         {
             file.delete();
             return FileVisitResult.CONTINUE;
         }
         @Override
         public FileVisitResult postVisitDirectory(Path dir, IOException e)
             throws IOException
         {
             if (e != null) {
                 // directory iteration failed
                 throw e;
             }
             dir.delete();
             return FileVisitResult.CONTINUE;
         }
     });
 

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
             {
                 try {
                     dir.copyTo(target.resolve(source.relativize(dir)));
                 } catch (FileAlreadyExistsException e) {
                      // ignore
                 }
                 return CONTINUE;
             }
             @Override
             public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                 throws IOException
             {
                 file.copyTo(target.resolve(source.relativize(file)));
                 return CONTINUE;
             }
         });
 

Since:

1.7

Method Summary

Modifier and Type	Method and 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 Detail

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