code: public static String createSubsetPrefix() {
      	StringBuilder sb = new StringBuilder(8);
          
          for (int k = 0; k < 6; ++k) {
              sb.append( (char)(Math.random() * 26 + 'A') );
          }
          sb.append("+");
          return sb.toString();
      }
docs: Creates a unique subset prefix to be added to the font name when the font is embedded and subset.
  @return the subset prefix