return BigInteger.equals(this, (BigInteger) obj);
for (int i = x.ival; --i >= 0; ) { if (x.words[i] != y.words[i]) return false; } return true;
  public boolean equals(Object obj)  {    if (obj == null || ! (obj instanceof BigInteger))      return false;    return BigInteger.equals(this, (BigInteger) obj);  }