They both increment the number.
++i is equivalent to
i = i + 1.
++i are very similar but not exactly the same. Both increment the number, but
++i increments the number before the current expression is evaluted, whereas
i++ increments the number after the expression is evaluated.
int i = 3; int a = i++; //a = 3, i = 4 int b = ++a; //b = 4, a = 4