code: public static void isFile(File parameter, String name) throws IllegalArgumentException {
  		if (parameter == null || !parameter.exists() || parameter.isDirectory()) {
  			throw new IllegalArgumentException(String.format("%s |%s| is missing or is a directory.", name, parameter.getAbsolutePath()));
  		}
  	}
docs: Check if file parameter is an existing ordinary file, not a directory. This validator throws illegal argument if given
  file does not exist or is not an ordinary file.
  
  @param parameter invocation file parameter,
  @param name parameter name.
  @throws IllegalArgumentException if <code>parameter</code> file is null or does not exist or is a directory.