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	/*
	* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* 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).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	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
	* {@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.
	*
	* <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.
	*
	* @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.
	*
	* @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 {@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;
	}

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