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

You could take advantage of ASCII value for each letter and take off 55, easy and fast:

int asciiOffset = 55;
char hex = Character.toUpperCase('A');  // Only A-F uppercase
int val = hex - asciiOffset;
System.out.println("hexadecimal:" + hex);
System.out.println("decimal:" + val);

Output:
hexadecimal:A
decimal:10