JAVA: Converting BigInteger to array of numbers

Question

I have a biginteger

BigInteger b = new BigInteger("2389623956378561348065123807561278905618906");

And I need to print all its digits (2, 3, 8, and so on...). How can I do it?

Answer 1

Already answered by Evan Knowles and user3322273, but here is another implementation:

byte[] digits = b.getBytes();
for (byte digit : digits) {
    System.out.println (digit & 0xf);
}

What it does is that it masks the (ASCII) value of the digit. For example:

'0' = 48     | In ASCII and Unicode - Decimal
    = 110000 | In binary

Hence, if we obtain the last four bits, then we can get the number. So

48 & 0xf (i.e. 15)
= 11 0000
& 00 1111
=    0000
=    0   | Ultimately in decimal.

Answer 2

Convert to char array, then decrease from each char the ASCII code of '0' char, to get digits between 0 and 9

char[] digits = b.toString().toCharArray();
for (char digit : digits) {
    digit -= '0';
    System.out.println((int)digit);
}

Note that if you just want to print, don't reduce the '0' ASCII value, and don't cast to int when printing