NioFileCopy.java

package com.anma.java.core.nio;

import java.io.IOException;
import java.nio.file.*;
import java.nio.file.attribute.BasicFileAttributes;
import java.nio.file.attribute.FileTime;
import java.util.EnumSet;

import static java.nio.file.FileVisitResult.CONTINUE;
import static java.nio.file.FileVisitResult.SKIP_SUBTREE;
import static java.nio.file.StandardCopyOption.COPY_ATTRIBUTES;
import static java.nio.file.StandardCopyOption.REPLACE_EXISTING;

public class NioFileCopy {
        /**
         * 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);
                }
            }
        }
}