8187443: Forest Consolidation: Move files to unified layout

Reviewed-by: darcy, ihse

src/java.base/share/classes/java/nio/file/FileVisitor.java

@@ -0,0 +1,177 @@
+/*
+ * 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&lt;Path&gt;() {
+ *         &#64;Override
+ *         public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
+ *             throws IOException
+ *         {
+ *             Files.delete(file);
+ *             return FileVisitResult.CONTINUE;
+ *         }
+ *         &#64;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&lt;Path&gt;() {
+ *             &#64;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;
+ *             }
+ *             &#64;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;
+}