hex - Java - Convert Big-Endian to Little-Endian -

i have following hex string:

00000000000008a3a41b85b8b29ad444def299fee21793cd8b9e567eab02cd81

but want this:

81cd02ab7e569e8bcd9317e2fe99f2de44d49ab2b8851ba4a308000000000000 (big endian)

i think have reverse , swap string, doesn't give me right result:

  string hex = "00000000000008a3a41b85b8b29ad444def299fee21793cd8b9e567eab02cd81";     hex = new stringbuilder(hex).reverse().tostring(); 

result: 81dc20bae765e9b8dc39712eef992fed444da92b8b58b14a3a80000000000000 (wrong) 81cd02ab7e569e8bcd9317e2fe99f2de44d49ab2b8851ba4a308000000000000 (should be)

the swapping:

    public static string hexswap(string orighex) {         // make number hex         biginteger orig = new biginteger(orighex,16);         // bytes swap         byte[] origbytes = orig.tobytearray();         int = 0;         while(origbytes[i] == 0) i++;         // swap bytes         byte[] swapbytes = new byte[origbytes.length];         for(/**/; < origbytes.length; i++) {             swapbytes[i] = origbytes[origbytes.length - - 1];         }         biginteger swap = new biginteger(swapbytes);         return swap.tostring(10);     }  hex = hexswap(hex); 

result: 026053973026883595670517176393898043396144045912271014791797784 (wrong) 81cd02ab7e569e8bcd9317e2fe99f2de44d49ab2b8851ba4a308000000000000 (should be)

can give me example of how accomplish this? thank lot :)

you need swap each pair of characters, you're reversing order of bytes, not nybbles. like:

public static string reversehex(string originalhex) {     // todo: validation length     int lengthinbytes = originalhex.length() / 2;     char[] chars = new char[lengthinbytes * 2];     (int index = 0; index < lengthinbytes; index++) {         int reversedindex = lengthinbytes - 1 - index;         chars[reversedindex * 2] = originalhex.charat(index * 2);         chars[reversedindex * 2 + 1] = originalhex.charat(index * 2 + 1);     }     return new string(chars); }