code: public static Map<String, List<String>> toHashMap(final String aFilePath) throws FileNotFoundException {
          return toHashMap(aFilePath, null, (String[]) null);
      }
docs: Returns a Map representation of the supplied directory's structure. The map contains the file name as the key
  and its path as the value. If a file with a name occurs more than once, multiple path values are returned for
  that file name key. The map that is returned is unmodifiable.
  
  @param aFilePath The directory of which you'd like a file listing
  @return An unmodifiable map representing the files in the file structure
  @throws FileNotFoundException If the directory for the supplied file path does not exist