if (value == null) throw new NullPointerException();
  public synchronized boolean contains(Object value)  {    for (int i = buckets.length - 1; i >= 0; i--)      {        HashEntry<K, V> e = buckets[i];        while (e != null)          {            if (value.equals(e.value))              return true;            e = e.next;          }      }    // Must throw on null argument even if the table is empty    if (value == null)      throw new NullPointerException();    return false;    }