code: public String getUserID(String globusID) {
          String [] ids = getUserIDs(globusID);
          if (ids != null && ids.length > 0) {
              return ids[0];
          } else {
              return null;
          }
      }
docs: Returns first local user name mapped to the specified
  globusID.
  
  @param globusID globusID
  @return local user name for the specified globusID.
  Null if the globusID is not mapped
  to a local user name.