code: private static Path validatePath(Path path) {
  		final URI uri = path.toUri();
  		final String scheme = uri.getScheme();
  		final String pathPart = uri.getPath();
  
  		// some validity checks
  		if (scheme == null) {
  			throw new IllegalArgumentException("The scheme (hdfs://, file://, etc) is null. " +
  					"Please specify the file system scheme explicitly in the URI.");
  		}
  		if (pathPart == null) {
  			throw new IllegalArgumentException("The path to store the checkpoint data in is null. " +
  					"Please specify a directory path for the checkpoint data.");
  		}
  		if (pathPart.length() == 0 || pathPart.equals("/")) {
  			throw new IllegalArgumentException("Cannot use the root directory for checkpoints.");
  		}
  
  		return path;
  	}
docs: Checks the validity of the path's scheme and path.
  
  @param path The path to check.
  @return The URI as a Path.
  
  @throws IllegalArgumentException Thrown, if the URI misses scheme or path.