Flip a Hex String

Question

Acording to a other question made here Split a Hex String without spaces and flip it, I write this new question more clearly here.

I have an Hex String like this:

Hex_string = 2B00FFEC

What I need is to change the order of the Hex String to start from the latest characters, so this would be like this:

Fliped_hex_string = ECFF002B

In the other question I asked a way to achieve this using the .split() method. But there should be another way to get this in a better way.

Answer 1

As simple as you can is

    String s = "2B00FFEC";
    StringBuilder  result = new StringBuilder();
    for (int i = 0; i <=s.length()-2; i=i+2) {
        result.append(new StringBuilder(s.substring(i,i+2)).reverse());
     }
    System.out.println(result.reverse().toString());   //op :ECFF002B

Answer 2

OP constrains the character length to exactly 8 characters in comments.

A purely numeric answer (inspired from idioms to convert endianness); saves going to and from strings

n is an int:

int m = ((n>>24)&0xff) |       // byte 3 to byte 0
        ((n<<8)&0xff0000) |    // byte 1 to byte 2
        ((n>>8)&0xff00) |      // byte 2 to byte 1
        ((n<<24)&0xff000000);  // byte 0 to byte 3

If you need to convert this to hexadecimal, use

String s = Integer.toHexString(m);

and if you need to set n from hexadecimal, use

int n = (int)Long.parseLong(hex_string, 16);

where hex_string is your initial string. You need to go via the Long parser to allow for negatives.