Integer.parseInt problems

Question

Hi everyone,
I want to use the Integer.parseInt and Byte.parseByte methods to parse hex strings - the problem is that they don't parse negative 2's complement numbers, they explicitly need a minus sign in front of an otherwise unsigned number to show that it's negative.
Examples:
//System.out.println(Integer.parseInt(Integer.toHexString(-1), 16)); //NumberFormatException
System.out.println(0xffffffff); // but this prints -1
//System.out.println(Byte.parseByte("ff", 16)); //NumberFormatException
System.out.println(Byte.parseByte("-1", 16)); // but this worksIs there some other method that will do what I need?
Regards,
Jonathan

Answer 1

Here's a dirty solution:public class Test {
    private static char[] digits = new char[] {
        '0', '1', '2', '3',
        '4', '5', '6', '7',
        '8', '9', 'a', 'b',
        'c', 'd', 'e', 'f'
    public static void main (String[] parameters) {
        String number = Integer.toHexString (parameters[0].equals ("+") ? Integer.MAX_VALUE : parameters[0].equals ("-") ? Integer.MIN_VALUE : Integer.parseInt (parameters[0]));
        if ((number.length () == 8) && (getPosition (number.charAt (0)) >= 8)) {
            String newNumber = "";
            for (int i = 0; i < number.length (); i ++) {
                newNumber += digits[15 - getPosition (number.charAt (i))];
            number = "";
            boolean carry = true;
            for (int i = 7; i >= 0; i --) {
                int position = getPosition (newNumber.charAt (i));
                if (carry) {
                    position = (position + 1) % 16;
                    carry = (position == 0);
                number = digits[position] + number;
            number = "-" + number;
        int numberAsInt;
        try {
            numberAsInt = Integer.parseInt (number, 16);
        } catch (NumberFormatException exception) {
            // -8000000
            numberAsInt = Integer.MIN_VALUE;
        System.out.println (numberAsInt);
    private static int getPosition (char digit) {
        int position = 0;
        while ((position < digits.length) && (digits[position] != digit)) {
            position ++;
        return position;
}Start with java Test <yourNumber>: + for Integer.MAX_VALUE, - for Integer.MIN_VALUE.
I don't claim it's good or efficient: it's working though. There's lots of things to improve.
Kind regards,
  Levi