code: public static String getMimeTypeFromExtension(String extension) {
          if (extension == null || extension.length() == 0) {
              return null;
          }
          return extensionToMimeTypeMap.get(extension);
      }
docs: Returns the MIME type for the given extension.
  
  @param extension A file extension without the leading '.'
  @return The MIME type for the given extension or null iff there is none.