What is '10' doing there?

Question

int num = 5542;
String number = String.valueOf(num);
for(int i = 0; i < number.length(); i++) {
int j = Character.digit(number.charAt(i), 10); System.out.println("digit: " + j);
}

Asking about the 10 in line 4.
I guess it's converting char into int..but am no sure!

Answer 1

I think it's used to convert it to particular number system => 10 is for decimal, 2 is for binary number etc.

Answer 2

Yea, 10 is converting 'j' in base 10 i.e equal to j but in an integer form.

Got it, thanks anyways
TheWh¡teCat