if (advanceTo(nextEntry) || nextInChain()) {
            return true;
          }
        }
      }
      return false;
    }

    /**
     * Advances to the given entry. Returns {@code true} if the entry was valid, {@code false} if it
     * should be skipped.
     */
    boolean advanceTo(E entry) {
      try {
        K key = entry.getKey();