How to convert a byte into a String that displays its hex value (0x0e -> "0E")

Question

So i have a piece of code, which converted byte[] from a binary file into int[] which then went on to be converted to String.

Example: 02 09 1A would translate to "2926" using String.valueOf(byte);

But this is where the fun begins: the old Code already split up the array before it became String so it didn't matter. Now i have code which needs to somehow figure out if there is a 2 9 or 29... How can i get the String to
- stay in Hex instead of "switching" to decimal and
- keep the zeros in the string
so i can always grab the next two chars, figure out which info they display and go on?

Input:
05 06 1D 11 07 08 01 32 21 28 2F 20 2E 21 34 22 25 33 01 02 09 0A FF 0B 0C
2!(/ .!4"%3 ÿ
Current Output: 562917781503340473246335234375112910-11112
Expected Output: 05061D110708013221282F202E21342225330102090AFF0B0C

(Didn't put my old code in here since it's based on int which is crap)

Can you show some inputs and outputs? Right now your question is not very clear. — Sweeper, May 23 '20 at 13:33
Added Input, expected and real output. Also to clarify: java makes FF -1 so the old code stopped reading here, but its inevidable to use FF at this point of the binary. — RAVN Mateus, May 23 '20 at 13:46
Is the input in a `byte[]`? Also, why is "2!(/ .!4"%3 ÿ" at the end of the input? — Sweeper, May 23 '20 at 13:49
Thanks for the answer, this code works exactly the way i wanted ^^ The reason this random stuff is at the end of input is, that i put the ASCII characters representing the hex value under the hex value so noone could think "05 " would be the bytes 0x30 0x35 0x20) — RAVN Mateus, May 23 '20 at 14:17

score 1 · Accepted Answer · answered May 23 '20 at 14:06

If I understand correctly, you have a byte[] as input, and you want to output a string that is all those bytes, in hex form, joined together:

private static String byteArrayToString(byte[] byteArray) {
    StringBuilder builder = new StringBuilder();
    for (byte b : byteArray) {
        int i = Byte.toUnsignedInt(b);
        if (i < 16) {
            builder.append("0");
        }
        builder.append(Integer.toHexString(i).toUpperCase());
    }
    return builder.toString();
}

Note the use of Byte.toUnsignedInt. This converts things like -1 the byte to the int 0xff. This is required because Java's bytes are signed.

Also note where I pad with 0. I only do this if the byte is a single digit in hex. i < 16 is the condition to check this.

score 1 · Answer 2 · answered May 23 '20 at 14:16

1

Another way:

  char[] hexVals = {'0', '1','2','3','4','5','6','7','8','9','A', 'B','C','D','E','F'};
  byte[] bytes = {5, 6, (byte)0xAB, (byte)0xde};   // sample input
  char[] output = new char[bytes.length*2];
  // split each byte's hex digits into two chars
  for(int i=0; i < bytes.length; i++) {
     output[2*i] = hexVals[(bytes[i] >> 4) & 0xf];  // HO nibble
     output[2*i+1] = hexVals[bytes[i] & 0xf];       // LO nibble
  }
  System.out.println(new String(output)); //  0506ABDE

answered May 23 '20 at 14:16

NormR

336
3
12

Also a pretty good solution, since i have to write the same code in Assembler, C, C++ and Java i will definitly make use of it in the other languages where i cant access the libraries. I will leave the accepted answer to Sweeper since this Post was decleared Java but thank you for showing me this (i cant access any libraries in c and assembler since the code is for reading header used in a java game and also for all kinds of files in my OS) :) – RAVN Mateus May 23 '20 at 15:10

How to convert a byte into a String that displays its hex value (0x0e -> "0E")

2 Answers2