public BigInteger(byte[] val)
private BigInteger()
  public BigInteger(byte[] val)  {    if (val == null || val.length < 1)      throw new NumberFormatException();    words = byteArrayToIntArray(val, val[0] < 0 ? -1 : 0);    BigInteger result = make(words, words.length);    this.ival = result.ival;    this.words = result.words;  }