Java example source code file (SkipSiblings.java)

This example Java source code file (SkipSiblings.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

basicfileattributes, filevisitresult, hashset, ioexception, override, path, random, runtimeexception, set, simplefilevisitor, skipsiblings, util

The SkipSiblings.java Java example source code

/*
 * Copyright (c) 2008, 2013, 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.
 */

/*
 * @test
 * @summary Unit test for Files.walkFileTree to test SKIP_SIBLINGS return value
 * @library ../..
 * @compile SkipSiblings.java CreateFileTree.java
 * @run main SkipSiblings
 */

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();

    // 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 {
        Path top = CreateFileTree.create();
        try {
            test(top);
        } finally {
            TestUtil.removeAll(top);
        }
    }

    static void test(final Path start) throws IOException {
        Files.walkFileTree(start, 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);
                if (rand.nextBoolean()) {
                    return FileVisitResult.CONTINUE;
                } else {
                    return FileVisitResult.SKIP_SIBLINGS;
                }
            }
        });
    }
}