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?

Solution 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... :-)

Solution 2

Easiest way to do it with javax.xml.bind.DatatypeConverter:

    String hex = "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";
    byte[] s = DatatypeConverter.parseHexBinary(hex);
    System.out.println(new String(s));

Solution 3

String hexToAscii(String s) {
  int n = s.length();
  StringBuilder sb = new StringBuilder(n / 2);
  for (int i = 0; i < n; i += 2) {
    char a = s.charAt(i);
    char b = s.charAt(i + 1);
    sb.append((char) ((hexToInt(a) << 4) | hexToInt(b)));
  }
  return sb.toString();
}

private static int hexToInt(char ch) {
  if ('a' <= ch && ch <= 'f') { return ch - 'a' + 10; }
  if ('A' <= ch && ch <= 'F') { return ch - 'A' + 10; }
  if ('0' <= ch && ch <= '9') { return ch - '0'; }
  throw new IllegalArgumentException(String.valueOf(ch));
}

Solution 4

Check out Convert a string representation of a hex dump to a byte array using Java?

Disregarding encoding, etc. you can do new String (hexStringToByteArray("75546..."));

Solution 5

So as I understand it, you need to pull out successive pairs of hex digits, then decode that 2-digit hex number and take the corresponding char:

String s = "...";
StringBuilder sb = new StringBuilder(s.length() / 2);
for (int i = 0; i < s.length(); i+=2) {
    String hex = "" + s.charAt(i) + s.charAt(i+1);
    int ival = Integer.parseInt(hex, 16);
    sb.append((char) ival);
}
String string = sb.toString();

View more solutions