Convert string representation of a hexadecimal byte array to a string with non ascii characters in Java

The stuff within the square brackets, seems to be characters encoded in UTF-8 but converted into a hexadecimal string in a weird way. What you can do is find each instance that looks like [0xc3] and convert it into the corresponding byte, and then create a new string from the bytes.

Unfortunately there are no good tools for working with byte arrays. Here's a quick and dirty solution that uses regex to find and replace these hex codes with the corresponding character in latin-1, and then fixes that by re-interpreting the bytes.

String bracketDecode(String str) {
    Pattern p = Pattern.compile("\\[(0x[0-9a-f]{2})\\]");
    Matcher m = p.matcher(str);
    StringBuilder sb = new StringBuilder();
    while (m.find()) {
        String group = m.group(1);
        Integer decode = Integer.decode(group);
        // assume latin-1 encoding
        m.appendReplacement(sb, Character.toString(decode));
    }
    m.appendTail(sb);
    // oh no, latin1 is not correct! re-interpret bytes in utf-8
    byte[] bytes = sb.toString().getBytes(StandardCharsets.ISO_8859_1);
    return new String(bytes, StandardCharsets.UTF_8);
}