How could I have the index of an array 'roll over' when incrementing?

Question

So I have an Array with a length of 4. When I increment it by 1 and the number gets bigger than the length of the array, I\'d like it to rollover.

For example:

Answer 1

Divide the incremented index modulo the array's length:

current_index = (current_index + n) % textviewlist.length