Convert a String of Hex into ASCII in Java

Question

I hope this isn't too much of a stupid question, I have looked on 5 different pages of Google results but haven't been able to find anything on this.

What I need to do is convert a string that contains all Hex characters into ASCII for example

String fileName = 

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

Every way I have seen makes it seems like you have to put it into an array first. Is there no way to loop through each two and convert them?

Answer 1

Just use a for loop to go through each couple of characters in the string, convert them to a character and then whack the character on the end of a string builder:

String hex = "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";
StringBuilder output = new StringBuilder();
for (int i = 0; i < hex.length(); i+=2) {
    String str = hex.substring(i, i+2);
    output.append((char)Integer.parseInt(str, 16));
}
System.out.println(output);

Or (Java 8+) if you're feeling particularly uncouth, use the infamous "fixed width string split" hack to enable you to do a one-liner with streams instead:

System.out.println(Arrays
        .stream(hex.split("(?<=\\G..)")) //https://stackoverflow.com/questions/2297347/splitting-a-string-at-every-n-th-character
        .map(s -> Character.toString((char)Integer.parseInt(s, 16)))
        .collect(Collectors.joining()));

Either way, this gives a few lines starting with the following:

uTorrent\Completed\nfsuc_ost_by_mustang\Pendulum-9,000 Miles.mp3

Hmmm... :-)