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I have a String array that actually consists of Hex characters.

Let's say the contents are ->

String array[] = {8C,D9,26,1D,69,B7,96,DB};

Now I want these to be interpreted as Hex characters of 1 byte each and not as a String where each entry is 2 bytes.

StringBuilder output = new StringBuilder();
for (int j = 0; j < array.length; j++) {
        String temp = "\u00"+ array[j];
        output.append(temp);
    }

Tried something like that, but it's not possible because it keeps complaining about "illegal unicode escape". I tried using "\u00" (i.e. two backslashes before u, but stackoverflow displays only one there) instead of "\u00" to get around that error, but then I don't see the real Hex values in the array, instead I see a bunch of strings like -> "\U008C" , "\U00D9" and so on..

I want the after conversion values to be 0x8C, 0xD9, 0x26...

Thanks.

EDIT: I have updated the question, just to clarify there were no commas in the array itself. And eventually I need to put all those values together, and use that as a HMAC key that is a hex string and NOT a text string.

share|improve this question
So you want a byte[] as your output? Your example above is misleading if so since you are building a String. – cklab Jul 12 '12 at 2:16
I would do a getBytes() on it once I have the hex string in place. – highflyer Jul 12 '12 at 2:18
Unicode escapes like "\u20ac" are handled by the compiler at compile-time, so generating them in code with "\u00" + array[j] wouldn't do you any good, anyway. The first part of Bohemian's answer is what you need, I think. – David Conrad Jul 12 '12 at 3:00

3 Answers

up vote 3 down vote accepted

Let the JDK do the work for you:

String[] array = {"8C", "D9", "26", "1D", "69", "B7", "96", "DB"};

StringBuilder output = new StringBuilder();
for ( String hex : array ) {
    output.append( (char)Integer.parseInt( hex, 16 ) );
}

Basically just that one line inside the loop is all you need.

If you wanted your input to be just one big String (which would seem more convenient), just do this instead:

String input = "8CD9261D69B796DB";

StringBuilder output = new StringBuilder();
for ( String hex : input.replaceAll( "..(?!$)", "$0," ).split( "," ) ) {
    output.append( (char)Integer.parseInt( hex, 16 ) );
}

Edited:

If you want byte[] result, do this:

String[] array = {"8C", "D9", "26", "1D", "69", "B7", "96", "DB"};

byte[] bytes = new byte[array.length];
for ( int i = 0; i < array.length; i++ ) {
    bytes[i] = (byte)Integer.parseInt( array[i], 16 );
}
share|improve this answer
@highflyer Since you want a byte[], you can use Integer.valueOf(hex, 16).byteValue(); to go directly to a byte as opposed to creating a String to convert to a byte[]. – cklab Jul 12 '12 at 2:23
@cklab Perfect! I did what you suggested and it worked like a charm! Although Bohemian's answer is correct as well but cklab's solution got me the eventual value I was looking for, probably doing getBytes() later was messing me up. Thanks guys :) – highflyer Jul 12 '12 at 2:30
See edited answer for the simplest way to get byte[] – Bohemian Jul 12 '12 at 2:34
@Bohemian Yes, that works as well. Thank you! – highflyer Jul 12 '12 at 2:44
up vote 0 down vote

Use the String.split method to split on the ,

For each element in the returned array go data[i] = "0x" + data[i];

For each element in the array str += data[i]

EZ

share|improve this answer
up vote 0 down vote

You can split it as follows: 

public static void main(String[] args) {
    String givenString = "8C,D9,26,1D,69,B7,96,DB";
    String[] splitString = givenString.split("[,]");

    for(int index = 0; index < splitString.length; index++){
        System.out.print("0x"+ splitString[index]);
        System.out.print((index == splitString.length - 1) ? "":",");
    }
    System.out.println();

}

For joining them, well instead of my System.out statements, use StringBuilder or StringBuffer and append to it.

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