178 lines
6.4 KiB
Java
178 lines
6.4 KiB
Java
/*
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* Copyright (c) 2007, 2011, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.nio.file;
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import java.nio.file.attribute.BasicFileAttributes;
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import java.io.IOException;
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/**
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* A visitor of files. An implementation of this interface is provided to the
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* {@link Files#walkFileTree Files.walkFileTree} methods to visit each file in
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* a file tree.
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*
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* <p> <b>Usage Examples:</b>
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* Suppose we want to delete a file tree. In that case, each directory should
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* be deleted after the entries in the directory are deleted.
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* <pre>
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* Path start = ...
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* Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
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* @Override
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* public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
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* throws IOException
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* {
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* Files.delete(file);
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* return FileVisitResult.CONTINUE;
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* }
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* @Override
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* public FileVisitResult postVisitDirectory(Path dir, IOException e)
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* throws IOException
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* {
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* if (e == null) {
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* Files.delete(dir);
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* return FileVisitResult.CONTINUE;
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* } else {
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* // directory iteration failed
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* throw e;
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* }
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* }
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* });
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* </pre>
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* <p> Furthermore, suppose we want to copy a file tree to a target location.
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* In that case, symbolic links should be followed and the target directory
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* should be created before the entries in the directory are copied.
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* <pre>
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* final Path source = ...
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* final Path target = ...
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*
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* Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE,
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* new SimpleFileVisitor<Path>() {
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* @Override
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* public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
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* throws IOException
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* {
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* Path targetdir = target.resolve(source.relativize(dir));
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* try {
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* Files.copy(dir, targetdir);
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* } catch (FileAlreadyExistsException e) {
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* if (!Files.isDirectory(targetdir))
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* throw e;
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* }
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* return CONTINUE;
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* }
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* @Override
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* public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
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* throws IOException
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* {
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* Files.copy(file, target.resolve(source.relativize(file)));
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* return CONTINUE;
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* }
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* });
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* </pre>
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*
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* @since 1.7
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*/
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public interface FileVisitor<T> {
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/**
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* Invoked for a directory before entries in the directory are visited.
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*
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* <p> If this method returns {@link FileVisitResult#CONTINUE CONTINUE},
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* then entries in the directory are visited. If this method returns {@link
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* FileVisitResult#SKIP_SUBTREE SKIP_SUBTREE} or {@link
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* FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS} then entries in the
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* directory (and any descendants) will not be visited.
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*
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* @param dir
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* a reference to the directory
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* @param attrs
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* the directory's basic attributes
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*
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* @return the visit result
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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FileVisitResult preVisitDirectory(T dir, BasicFileAttributes attrs)
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throws IOException;
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/**
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* Invoked for a file in a directory.
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*
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* @param file
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* a reference to the file
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* @param attrs
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* the file's basic attributes
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*
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* @return the visit result
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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FileVisitResult visitFile(T file, BasicFileAttributes attrs)
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throws IOException;
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/**
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* Invoked for a file that could not be visited. This method is invoked
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* if the file's attributes could not be read, the file is a directory
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* that could not be opened, and other reasons.
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*
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* @param file
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* a reference to the file
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* @param exc
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* the I/O exception that prevented the file from being visited
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*
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* @return the visit result
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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FileVisitResult visitFileFailed(T file, IOException exc)
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throws IOException;
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/**
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* Invoked for a directory after entries in the directory, and all of their
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* descendants, have been visited. This method is also invoked when iteration
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* of the directory completes prematurely (by a {@link #visitFile visitFile}
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* method returning {@link FileVisitResult#SKIP_SIBLINGS SKIP_SIBLINGS},
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* or an I/O error when iterating over the directory).
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*
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* @param dir
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* a reference to the directory
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* @param exc
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* {@code null} if the iteration of the directory completes without
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* an error; otherwise the I/O exception that caused the iteration
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* of the directory to complete prematurely
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*
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* @return the visit result
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*
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* @throws IOException
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* if an I/O error occurs
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*/
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FileVisitResult postVisitDirectory(T dir, IOException exc)
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throws IOException;
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}
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