/*

 * Copyright (c) 2008, 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.

 *

 * 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.

 */

import java.nio.file.*;

import java.nio.file.attribute.*;

import java.io.IOException;

import java.util.*;

public class SkipSiblings {

    static final Random rand = new Random();

    static final Set<Path> skipped = new HashSet<Path>();

    // check if this path's directory has been skipped

    static void check(Path path) {

        if (skipped.contains(path.getParent()))

            throw new RuntimeException(path + " should not have been visited");

    }

    // indicates if the siblings of this path should be skipped

    static boolean skip(Path path) {

        Path parent = path.getParent();

        if (parent != null && rand.nextBoolean()) {

            skipped.add(parent);

            return true;

        }

        return false;

    }

    public static void main(String[] args) throws Exception {

        Files.walkFileTree(dir, new SimpleFileVisitor<Path>() {

            @Override

            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {

                check(dir);

                if (skip(dir))

                    return FileVisitResult.SKIP_SIBLINGS;

                return FileVisitResult.CONTINUE;

            }

            @Override

            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {

                check(file);

                if (skip(file))

                    return FileVisitResult.SKIP_SIBLINGS;

                return FileVisitResult.CONTINUE;

            }

            @Override

            public FileVisitResult postVisitDirectory(Path dir, IOException x) {

                if (x != null)

                    throw new RuntimeException(x);

                check(dir);

            }

        });

    }

}