Exception within a condition

I'm solving an exercise on leetcode which is to write a solution that takes strings of variable length and returns a modified version of them. In the course of my code, I want to use if statements with conditionals like if (my_string[i+j]==my_string[i-j]). But my_string[i+j] may cause an out of range error.

Is it good practice to do this, if you as the coder want an exception to evaluate to false?