private String concatenateExtraParams() {
      final StringBuilder sb = new StringBuilder();
      boolean first = true;
      for (Entry<String, String> entry : extraParams.entrySet()) {
        if (entry.getKey() != null && entry.getValue() != null) {
          if (!first) {
            sb.append(',');
          }
          first = false;
          sb.append(entry.getKey() + '=');
          sb.append(entry.getValue());
        }
      }
      return sb.toString();
    }
Returns extra parameter key/value string
hbase-server/src/main/java/org/apache/hadoop/hbase/security/access/AuthResult.java