Convert hex to decimal

Hex2Dec.java

import java.text.NumberFormat;

public class Hex2Dec {

    public static int hexToDec(String hex) {

        String hexStr = hex.toUpperCase();
        if( hexStr.startsWith(("0x")))
            hexStr = hexStr.substring(2,hexStr.length()-1);

        int len = hexStr.length();
        int power = 0;
        int value = 0;
        for(int i=0; i<hexStr.length(); i++) {
            char c = hexStr.charAt(i);
            power = (int)Math.pow(16, len - 1);
            if( c >='0' && c <='9' )
                value += power * (c - 48);
            else if( c >='A' && c <= 'F' )
                value += power * (c - 65 + 10);
            len--;
        }
        return  value;
    }
    public static void main(String[] args) {
        if( args.length == 0 ) {
            System.out.println("Usage: java Hex2Dec <hex number>");
            return;
        }
        String hex = args[0];
        int value = hexToDec(hex);
        String valStr = NumberFormat.getInstance().format(value);
        System.out.println("0x" + hex.toUpperCase() + " = " + valStr);
    }
}