Java 8: Copy directory recursively?

Question

I see that Java 8 has significantly cleaned up reading the contents of a file into a String:

String contents = new String(Files.readAllBytes(Paths.get(new URI(so         


        

Answer 1

This version uses Files.walk and Path parameters as Java 8 suggests.

public static void copyFolder(Path src, Path dest) {
    try {
        Files.walk( src ).forEach( s -> {
            try {
                Path d = dest.resolve( src.relativize(s) );
                if( Files.isDirectory( s ) ) {
                    if( !Files.exists( d ) )
                        Files.createDirectory( d );
                    return;
                }
                Files.copy( s, d );// use flag to override existing
            } catch( Exception e ) {
                e.printStackTrace();
            }
        });
    } catch( Exception ex ) {
        ex.printStackTrace();
    }
}

Answer 2

Using Files.walkFileTree:

• you don't need to worry about closing Streams.
  (some other answers here forget that while using Files.walk)
• handles IOException elegantly.
  (Some other answers here would become more difficult when adding proper exception handling instead of a simple printStackTrace)

    public void copyFolder(Path source, Path target, CopyOption... options)
            throws IOException {
        Files.walkFileTree(source, new SimpleFileVisitor<Path>() {

            @Override
            public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                    throws IOException {
                createDirectories(target.resolve(source.relativize(dir)));
                return FileVisitResult.CONTINUE;
            }

            @Override
            public FileVisitResult visitFile(Path file, BasicFileAttributes attrs)
                    throws IOException {
                copy(file, target.resolve(source.relativize(file)), options);
                return FileVisitResult.CONTINUE;
            }
        });
    }

What this does is

• walk recursively over all files in the directory.
• When a directory is encountered (preVisitDirectory):
  create the corresponding one in the target directory.
• When a regular file is encountered (visitFile):
  copy it.

options can be used to tailor the copy to your needs. For example to overwrite existing files in the target directory, use copyFolder(source, target, StandardCopyOption.REPLACE_EXISTING);

Answer 3

In this way the code looks a bit simpler

import static java.nio.file.StandardCopyOption.*;

public  void copyFolder(Path src, Path dest) throws IOException {
    try (Stream<Path> stream = Files.walk(src)) {
        stream.forEach(source -> copy(source, dest.resolve(src.relativize(source))));
    }
}

private void copy(Path source, Path dest) {
    try {
        Files.copy(source, dest, REPLACE_EXISTING);
    } catch (Exception e) {
        throw new RuntimeException(e.getMessage(), e);
    }
}

Answer 4

How about the following code

public void copyFolder(File src, File dest) throws IOException {
        try (Stream<Path> stream = Files.walk(src.toPath())) {
            stream.forEachOrdered(sourcePath -> {

                try {
                    Files.copy(
                            /*Source Path*/
                            sourcePath,
                            /*Destination Path */
                            src.toPath().resolve(dest.toPath().relativize(sourcePath)));
                } catch (IOException e) {
                    throw new UncheckedIOException(e);
                }
            });
        }
    }

Answer 5

and one more version:

static void copyFolder(File src, File dest){
    // checks
    if(src==null || dest==null)
        return;
    if(!src.isDirectory())
        return;
    if(dest.exists()){
        if(!dest.isDirectory()){
            //System.out.println("destination not a folder " + dest);
            return;
        }
    } else {
        dest.mkdir();
    }

    if(src.listFiles()==null || src.listFiles().length==0)
        return;

    String strAbsPathSrc = src.getAbsolutePath();
    String strAbsPathDest = dest.getAbsolutePath();

    try {
        Files.walkFileTree(src.toPath(), new SimpleFileVisitor<Path>() {
            @Override
            public FileVisitResult visitFile(Path file,
                    BasicFileAttributes attrs) throws IOException {
                File dstFile = new File(strAbsPathDest + file.toAbsolutePath().toString().substring(strAbsPathSrc.length()));
                if(dstFile.exists())
                    return FileVisitResult.CONTINUE;

                if(!dstFile.getParentFile().exists())
                    dstFile.getParentFile().mkdirs();

                //System.out.println(file + " " + dstFile.getAbsolutePath());
                Files.copy(file, dstFile.toPath());

                return FileVisitResult.CONTINUE;
            }
        });

    } catch (IOException e) {
        //e.printStackTrace();
        return;
    }

    return;
}

its code use java8 Files.walkFileTree function.

Answer 6

my version:

static private void copyFolder(File src, File dest) {
    // checks
    if(src==null || dest==null)
        return;
    if(!src.isDirectory())
        return;
    if(dest.exists()){
        if(!dest.isDirectory()){
            //System.out.println("destination not a folder " + dest);
            return;
        }
    } else {
        dest.mkdir();
    }

    File[] files = src.listFiles();
    if(files==null || files.length==0)
        return;

    for(File file: files){
        File fileDest = new File(dest, file.getName());
        //System.out.println(fileDest.getAbsolutePath());
        if(file.isDirectory()){
            copyFolder(file, fileDest);
        }else{
            if(fileDest.exists())
                continue;

            try {
                Files.copy(file.toPath(), fileDest.toPath());
            } catch (IOException e) {
                //e.printStackTrace();
            }
        }
    }
}