To me this looks like a duplicate of Monitor subfolders with a Java watch service

You can watch subdirectories like this:

/**
 * Register the given directory, and all its sub-directories, with the WatchService.
 */
private void registerAll(final Path start) throws IOException {
    // register directory and sub-directories
    Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
            throws IOException {
                dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
                return FileVisitResult.CONTINUE;
        }
    });
}

To me this looks like a duplicate of Monitor subfolders with a Java watch service

You can watch subdirectories like this:

/**
 * Register the given directory, and all its sub-directories, with the WatchService.
 */
private void registerAll(final Path start) throws IOException {
    // register directory and sub-directories
    Files.walkFileTree(start, new SimpleFileVisitor<Path>() {
        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs)
            throws IOException {
                dir.register(watcher, ENTRY_CREATE, ENTRY_DELETE, ENTRY_MODIFY);
                return FileVisitResult.CONTINUE;
        }
    });
}