Without spoon-feeding you the code:
The nth digit is the remainder after dividing (a
divided by 10b-1) by 10.
return a / (int)Math.pow(10, b - 1) % 10;
See live demo.
If you want an iterative approach:
Loop b-1 times, each time assigning to the a
variable the result of dividing a
by 10.
After looping, the nth digit is the remainder of dividing a
by 10.
while (--b > 0) {
a /= 10;
}
return a % 10;
See live demo.
--
FYI The remainder operator is %
, so eg 32 % 10
returns 2
, and integer division drops remainders, so eg 32 / 10
returns 3
.