Java example source code file (Copy.java)

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Java - Java tags/keywords

basicfileattributes, continue, copy_attributes, copyoption, enumset, filesystemloopexception, filevisitor, filevisitresult, ioexception, override, path, replace_existing, string, treecopier, util

The Copy.java Java example source code

/*
 * Copyright (c) 2008, 2011, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 *
 *   - Neither the name of Oracle nor the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/*
 * This source code is provided to illustrate the usage of a given feature
 * or technique and has been deliberately simplified. Additional steps
 * required for a production-quality application, such as security checks,
 * input validation and proper error handling, might not be present in
 * this sample code.
 */


import java.nio.file.*;
import static java.nio.file.StandardCopyOption.*;
import java.nio.file.attribute.*;
import static java.nio.file.FileVisitResult.*;
import java.io.IOException;
import java.util.*;

/**
 * Sample code that copies files in a similar manner to the cp(1) program.
 */

public class Copy {

    /**
     * Returns {@code true} if okay to overwrite a  file ("cp -i")
     */
    static boolean okayToOverwrite(Path file) {
        String answer = System.console().readLine("overwrite %s (yes/no)? ", file);
        return (answer.equalsIgnoreCase("y") || answer.equalsIgnoreCase("yes"));
    }

    /**
     * Copy source file to target location. If {@code prompt} is true then
     * prompt user to overwrite target if it exists. The {@code preserve}
     * parameter determines if file attributes should be copied/preserved.
     */
    static void copyFile(Path source, Path target, boolean prompt, boolean preserve) {
        CopyOption[] options = (preserve) ?
            new CopyOption[] { COPY_ATTRIBUTES, REPLACE_EXISTING } :
            new CopyOption[] { REPLACE_EXISTING };
        if (!prompt || Files.notExists(target) || okayToOverwrite(target)) {
            try {
                Files.copy(source, target, options);
            } catch (IOException x) {
                System.err.format("Unable to copy: %s: %s%n", source, x);
            }
        }
    }

    /**
     * A {@code FileVisitor} that copies a file-tree ("cp -r")
     */
    static class TreeCopier implements FileVisitor<Path> {
        private final Path source;
        private final Path target;
        private final boolean prompt;
        private final boolean preserve;

        TreeCopier(Path source, Path target, boolean prompt, boolean preserve) {
            this.source = source;
            this.target = target;
            this.prompt = prompt;
            this.preserve = preserve;
        }

        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
            // before visiting entries in a directory we copy the directory
            // (okay if directory already exists).
            CopyOption[] options = (preserve) ?
                new CopyOption[] { COPY_ATTRIBUTES } : new CopyOption[0];

            Path newdir = target.resolve(source.relativize(dir));
            try {
                Files.copy(dir, newdir, options);
            } catch (FileAlreadyExistsException x) {
                // ignore
            } catch (IOException x) {
                System.err.format("Unable to create: %s: %s%n", newdir, x);
                return SKIP_SUBTREE;
            }
            return CONTINUE;
        }

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
            copyFile(file, target.resolve(source.relativize(file)),
                     prompt, preserve);
            return CONTINUE;
        }

        @Override
        public FileVisitResult postVisitDirectory(Path dir, IOException exc) {
            // fix up modification time of directory when done
            if (exc == null && preserve) {
                Path newdir = target.resolve(source.relativize(dir));
                try {
                    FileTime time = Files.getLastModifiedTime(dir);
                    Files.setLastModifiedTime(newdir, time);
                } catch (IOException x) {
                    System.err.format("Unable to copy all attributes to: %s: %s%n", newdir, x);
                }
            }
            return CONTINUE;
        }

        @Override
        public FileVisitResult visitFileFailed(Path file, IOException exc) {
            if (exc instanceof FileSystemLoopException) {
                System.err.println("cycle detected: " + file);
            } else {
                System.err.format("Unable to copy: %s: %s%n", file, exc);
            }
            return CONTINUE;
        }
    }

    static void usage() {
        System.err.println("java Copy [-ip] source... target");
        System.err.println("java Copy -r [-ip] source-dir... target");
        System.exit(-1);
    }

    public static void main(String[] args) throws IOException {
        boolean recursive = false;
        boolean prompt = false;
        boolean preserve = false;

        // process options
        int argi = 0;
        while (argi < args.length) {
            String arg = args[argi];
            if (!arg.startsWith("-"))
                break;
            if (arg.length() < 2)
                usage();
            for (int i=1; i<arg.length(); i++) {
                char c = arg.charAt(i);
                switch (c) {
                    case 'r' : recursive = true; break;
                    case 'i' : prompt = true; break;
                    case 'p' : preserve = true; break;
                    default : usage();
                }
            }
            argi++;
        }

        // remaining arguments are the source files(s) and the target location
        int remaining = args.length - argi;
        if (remaining < 2)
            usage();
        Path[] source = new Path[remaining-1];
        int i=0;
        while (remaining > 1) {
            source[i++] = Paths.get(args[argi++]);
            remaining--;
        }
        Path target = Paths.get(args[argi]);

        // check if target is a directory
        boolean isDir = Files.isDirectory(target);

        // copy each source file/directory to target
        for (i=0; i<source.length; i++) {
            Path dest = (isDir) ? target.resolve(source[i].getFileName()) : target;

            if (recursive) {
                // follow links when copying files
                EnumSet<FileVisitOption> opts = EnumSet.of(FileVisitOption.FOLLOW_LINKS);
                TreeCopier tc = new TreeCopier(source[i], dest, prompt, preserve);
                Files.walkFileTree(source[i], opts, Integer.MAX_VALUE, tc);
            } else {
                // not recursive so source must not be a directory
                if (Files.isDirectory(source[i])) {
                    System.err.format("%s: is a directory%n", source[i]);
                    continue;
                }
                copyFile(source[i], dest, prompt, preserve);
            }
        }
    }
}