DirectoryNotEmptyException while copying files

I wrote a program, where you can backup file or directory to chosen folder. Here is piece of my code:

try {
    if (srcFileOrDir.isFile()) {
        File destFile = new File(destDir.getAbsolutePath() + File.separator + srcFileOrDir.getName());
        Files.copy(srcFileOrDir.toPath(), destFile.toPath(), StandardCopyOption.REPLACE_EXISTING);
    }
    else { //isDirectory
        String[] pathParts = srcFileOrDir.getAbsolutePath().split("\\\\");
        destDir = new File(destDir.getAbsolutePath() + File.separator + pathParts[pathParts.length-1]);
        Files.walk(srcFileOrDir.toPath()).forEach(source -> {
            Path destination = destDir.toPath().resolve(srcFileOrDir.toPath().relativize(source));
            try {
                Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
            } catch (IOException e) {
                e.printStackTrace();
            }
        });
    }
    JOptionPane.showMessageDialog(null, "Backup was created successfully at " +       destDir.getAbsolutePath(), "Success!", JOptionPane.INFORMATION_MESSAGE);
}
catch (IOException e) {
    e.printStackTrace();
}

The problem is that program throws DirecroryNotEmptyException when i am trying to execute Files.copy(). The exception is thrown only if i am trying to backup directory. If i am backuping file everything works normal.

I used REPLACE_EXISTING option, but my program ignores it. Thanks in advance.

Your code will only handle directory copying to a new location. See the documentation of Files.copy:

> throws DirectoryNotEmptyException - the REPLACE_EXISTING option is
> specified but the file cannot be replaced because it is a non-empty
> directory

Therefore it is unnecessary to copy a directory that exists, just prefix copy line by checking !isDirectory() beforehand.

if (!Files.isDirectory(destination)) {
    System.out.format("Files.copy(%s, %s)%n",source, destination);
    Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
}

It is also unnecessary to test for srcFileOrDir.isFile() as Files.walk works for file or directory. Put that all together with exception handling, no path splitting, and clean new Path only method:

private static void copyToDirectory(Path src, Path destDir) throws IOException {
    final Path dest = destDir.resolve(src.getFileName());
    System.out.format("copying %s => %s%n",src, dest);
    Files.walk(src).forEach(source -> {
        Path destination = dest.resolve(src.relativize(source));
        try {
            if (!Files.isDirectory(destination)) {
                System.out.format("Files.copy(%s, %s)%n",source, destination);
                Files.copy(source, destination, StandardCopyOption.REPLACE_EXISTING);
            }
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    });
}