private int keyAt(int i) {
      try {
        if (DO_SANITY_CHECK) {
          if (isHashedLeaf()) {
            assert i < hashPageCapacity;
          }
          else {
            assert i < getChildrenCount();
          }
        }
        return getInt(indexToOffset(i) + KEY_OFFSET);
      }
      catch (IOException e) {
        throw new RuntimeException(e);
      }
    }
private int keyAt(int i)