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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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*
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package java.nio.file;
import java.nio.file.attribute.BasicFileAttributes;
import java.io.IOException;
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;
}
});
Since: 1.7
/**
* A visitor of files. An implementation of this interface is provided to the
* {@link Files#walkFileTree Files.walkFileTree} methods to visit each file in
* a file tree.
*
* <p> <b>Usage Examples:</b>
* Suppose we want to delete a file tree. In that case, each directory should
* be deleted after the entries in the directory are deleted.
* <pre>
* 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;
* }
* }
* });
* </pre>
* <p> 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.
* <pre>
* 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;
* }
* });
* </pre>
*
* @since 1.7
*/
public interface FileVisitor<T> {
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.
Params: - dir –
a reference to the directory
- attrs –
the directory's basic attributes
Throws: - IOException –
if an I/O error occurs
Returns: the visit result
/**
* Invoked for a directory before entries in the directory are visited.
*
* <p> If this method returns {@link FileVisitResult#CONTINUE CONTINUE},
* then entries in the directory are visited. If this method returns {@link
* FileVisitResult#SKIP_SUBTREE SKIP_SUBTREE} or {@link
* FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS} then entries in the
* directory (and any descendants) will not be visited.
*
* @param dir
* a reference to the directory
* @param attrs
* the directory's basic attributes
*
* @return the visit result
*
* @throws IOException
* if an I/O error occurs
*/
FileVisitResult preVisitDirectory(T dir, BasicFileAttributes attrs)
throws IOException;
Invoked for a file in a directory.
Params: - file –
a reference to the file
- attrs –
the file's basic attributes
Throws: - IOException –
if an I/O error occurs
Returns: the visit result
/**
* Invoked for a file in a directory.
*
* @param file
* a reference to the file
* @param attrs
* the file's basic attributes
*
* @return the visit result
*
* @throws IOException
* if an I/O error occurs
*/
FileVisitResult visitFile(T file, BasicFileAttributes attrs)
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.
Params: - file –
a reference to the file
- exc –
the I/O exception that prevented the file from being visited
Throws: - IOException –
if an I/O error occurs
Returns: the visit result
/**
* 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.
*
* @param file
* a reference to the file
* @param exc
* the I/O exception that prevented the file from being visited
*
* @return the visit result
*
* @throws IOException
* if an I/O error occurs
*/
FileVisitResult visitFileFailed(T file, 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). Params: - 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
Throws: - IOException –
if an I/O error occurs
Returns: the visit result
/**
* 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 {@link #visitFile visitFile}
* method returning {@link FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS},
* or an I/O error when iterating over the directory).
*
* @param dir
* a reference to the directory
* @param exc
* {@code 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
*
* @return the visit result
*
* @throws IOException
* if an I/O error occurs
*/
FileVisitResult postVisitDirectory(T dir, IOException exc)
throws IOException;
}