public void listFilesForFolder(final File folder) {
    for (final File fileEntry : folder.listFiles()) {
        if (fileEntry.isDirectory()) {
            listFilesForFolder(fileEntry);
        } else {
            System.out.println(fileEntry.getName());
        }
    }
}
final File folder = new File("/home/you/Desktop");
listFilesForFolder(folder);
Files. walk API is available from Java 8.
try (Stream<Path> paths = Files.walk(Paths.get("/home/you/Desktop"))) {
    paths
        .filter(Files::isRegularFile)
        .forEach(System.out::println);
} 
The example uses the try-with-resources pattern recommended in the API guide. It ensures that no matter the circumstances the stream will be closed.