I need to create a program for school where user inputs roman numbers and code outputs Arabic numbers. When I input V it outputs String index out of range: -1, but when I input I it works well, for context rimske = roman number, cisla = Arabic number
for (int i = 0; i <=rimske.length()-1 ; i++) {
switch (rimske.charAt(i)){
case 'I':
cislo++;
break;
case 'V':
cislo=cislo+5;
if (rimske.charAt(i-1) == 'I')
cislo = cislo - 2;
break;