code: public final void setKeyIds(String[] keyIds) {
          if (keyIds == null) {
              keyIds = ArrayUtils.EMPTY_STRING_ARRAY;
          }
          this.keyIds = keyIds.clone();
      }
docs: Sets the key ids to be queried. An array of length 0 or <code>null</code>
  means that all key ids will be queried.
  
  @param keyIds a {@link String[]} of key ids. If <code>null</code>, an
  empty {@link String[]} will be stored.