Java Utililty Methods File Copy nio

FileChannel fc1 = new FileInputStream(a).getChannel();
if (b.exists())
    b.delete();
FileChannel fc2 = new FileOutputStream(b).getChannel();
long count1 = fc1.size();
fc1.transferTo(0, count1, fc2);
fc1.close();
fc2.close();
...

File[] l = in.listFiles();
for (File f : l) {
    if (f.isDirectory()) {
        copy(base_path, f, out);
    } else {
        String relative_out = f.getAbsolutePath().replace(base_path.getAbsolutePath(), "");
        File dest_f = new File(out.getAbsolutePath() + relative_out);
        dest_f.mkdirs();
...

try {
    Files.copy(copied.toPath(), destination.toPath());
} catch (IOException e) {
    throw new Exception(copied.toString() + ": Can't copy");

if (file == null || !file.exists() || !file.canRead()) {
    throw new IOException("Unable to find source file to be copied " + file);
String basename = file.getName();
File destFile = new File(toDirectory, basename.toString());
if (!toDirectory.exists())
    toDirectory.createNewFile();
FileChannel fcSrc = null;
...

copy(from.toURI().toURL(), to);

if (!to.exists())
    to.createNewFile();
FileChannel fromChan = null;
FileChannel toChan = null;
try {
    fromChan = new FileInputStream(from).getChannel();
    toChan = new FileOutputStream(to).getChannel();
    toChan.transferFrom(fromChan, 0, fromChan.size());
...

try (FileInputStream fin = new FileInputStream(from);
        FileChannel in = fin.getChannel();
        FileOutputStream fout = new FileOutputStream(to);
        FileChannel out = fout.getChannel()) {
    in.transferTo(0, from.length(), out);
} catch (IOException e) {
    throw new RuntimeException(e);

final Path source = from.toPath();
final Path target = to.toPath();
if (recursive) {
    Files.walkFileTree(source, EnumSet.of(FileVisitOption.FOLLOW_LINKS), Integer.MAX_VALUE,
            new SimpleFileVisitor<Path>() {
                @Override
                public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
                        throws IOException {
...

if (in.exists() && in != null && out != null) {
    if (!out.exists()) {
        if (in.isDirectory()) {
            out.mkdirs();
        } else {
            out.createNewFile();
    String source = in.isDirectory() ? "directory" : "file";
    String target = out.isDirectory() ? "directory" : "file";
    if (!source.equals(target)) {
        throw new IOException("Can't duplicate " + source + " as " + target);
    } else {
        if (source.equals("directory")) {
            File[] files = in.listFiles();
            for (File file : files) {
                copy(file, new File(out, file.getName()));
        } else {
            FileChannel inCh = new FileInputStream(in).getChannel();
            FileChannel outCh = new FileOutputStream(out).getChannel();
            inCh.transferTo(0, inCh.size(), outCh);

if (overwrite || !out.exists() || (out.lastModified() < in.lastModified())) {
    FileChannel inChannel = new FileInputStream(in).getChannel();
    FileChannel outChannel = new FileOutputStream(out).getChannel();
    try {
        inChannel.transferTo(0, inChannel.size(), outChannel);
    } finally {
        if (inChannel != null) {
            inChannel.close();
...