code: public static LdapHelper getInstance(String instance) {
          if (!helpers.containsKey(instance)) {
              helpers.put(instance, new LdapHelper(instance));
          }
          LdapHelper helper = helpers.get(instance);
          if (!helper.online) {
              helper.loadProperties();
          }
          return helper;
      }
docs: Returns a new Instance of LdapHelper.
  
  @param instance the identifyer of the LDAP Instance (e.g. ldap1)
  @return a new Instance.