That way digits[0] will be the least significant digit for any given BigInteger, and digits[1] will always be the second, and so on. Rather than digits[2] for

That way digits[0] will be the least significant digit for any given BigInteger, and digits[1] will always be the second, and so on. Rather than digits[2] for -123's least significant digit, and digits[1] for, say, 43's least significant digit.