Converting Hexadecimal String to Decimal Integer

Question

I wrote some code to convert my hexadecimal display string to decimal integer. However, when input is something like 100a or 625b( something with letter) I got an error like

Answer 1

public class Hex2Decimal {

public static void hexDec(String num)
{
    int sum=0;
    int newnum = 0;
    String digit = num.toUpperCase();
    for(int i=0;i

public static void main(String[] args) {

hexDec("9F");

} }