public boolean containsValue(Object value)
  {
    if (value == null) return containsNullValue();

    Entry[] tab = this.table;
    for (int i = 0; i < tab.length; i++)
      for (Entry e = tab[i]; e != null; e = e.next)
        if (value.equals(e.value)) return true;
    return false;
  }