Java PatternSyntaxException: Illegal repetition on string substitution?

Question

I am trying to write a method that will accept a String, inspect it for instances of certain tokens (e.g. ${fizz}, ${buzz}, ${fo

Answer 1

As pointed out by Patashu, the problem is in replaceFirst(token, replacementValue), that expects a regex in the first argument, not a literal. Change it to replaceFirst(Pattern.quote(token), replacementValue) and you will do alright.

I also changed a bit the first regex, as it goes faster with + instead of * but that's not necessary.

static String substituteAllTokens(Map tokensMap, String toInspect) {
    String regex = "\\$\\{([^}]+)\\}";
    Pattern pattern = Pattern.compile(regex);
    Matcher matcher = pattern.matcher(toInspect);
    String result = toInspect;
    while(matcher.find()) {
        String token = matcher.group();     // Ex: ${fizz}
        String tokenKey = matcher.group(1); // Ex: fizz
        String replacementValue = null;

        if(tokensMap.containsKey(tokenKey))
            replacementValue = tokensMap.get(tokenKey);
        else
            throw new RuntimeException("String contained an unsupported token.");

        result = result.replaceFirst(Pattern.quote(token), replacementValue);
    }

    return result;
}