public static String toLZ( int i, int len )
   {
   // converts integer to left-zero padded string, len  chars long.
   String s = Integer.toString(i);
   if ( s.length() > len ) return s.substring(0,len);
   else if ( s.length() < len ) // pad on left with zeros
      return "000000000000000000000000000".substring(0, len - s.length ()) + s;
   else return s;
   } // end toLZ