int offset = pos >> 6; ensure(offset);   bits[offset] &= ~(1L << pos);
Arrays.fill(bits, 0);
  public void clear(int pos)  {    int offset = pos >> 6;    ensure(offset);    // ArrayIndexOutOfBoundsException subclasses IndexOutOfBoundsException,    // so we'll just let that be our exception.    bits[offset] &= ~(1L << pos);  }