code: public static synchronized int countEquivalentIDs(String id) {
          int count = 0;
          UResourceBundle res = openOlsonResource(null, id);
          if (res != null) {
              try {
                  UResourceBundle links = res.get("links");
                  int[] v = links.getIntVector();
                  count = v.length;
              } catch (MissingResourceException ex) {
                  // throw away
              }
          }
          return count;
      }
docs: Returns the number of IDs in the equivalency group that
  includes the given ID.  An equivalency group contains zones
  that behave identically to the given zone.
  
  <p>If there are no equivalent zones, then this method returns
  0.  This means either the given ID is not a valid zone, or it
  is and there are no other equivalent zones.
  @param id a system time zone ID
  @return the number of zones in the equivalency group containing
  'id', or zero if there are no equivalent zones.
  @see #getEquivalentID