Using functions or methods in Java's String.replaceAll() regex

Question

I am trying to convert an RPN-equation into a string that matches tigcc rules. There numbers must have the number of chars in front of them and a tag for positive or negative. For "2" it would be "1 2 POSINT_TAG"

My complete input to rpn converter is based on regexes, so I wanted to use them again and have a String.replaceAll() function like:

string.replaceAll("(\d+)","$1".length+" $1 POSINT_TAG");

But there it just prints: "2 number INT_TAG". I found some classes like com.stevesoft.pat (link).

Is there another way implemented in normal Sun Java to use (custom) functions in replace rules of regexes?

Answer 1

No, at least not the same way you would do it in C# or Ruby.

The closest thing is to write a loop like this:

static Pattern pattern = Pattern.compile("\\d+");
String convert(String input) {
    StringBuffer output = new StringBuffer();
    Matcher matcher = pattern.matcher(input);
    while (matcher.find()) {
        String rep =
            String.format("%d %s POSINT_TAG",
                          matcher.group().length(),
                          matcher.group());
        matcher.appendReplacement(output, rep);
    }
    matcher.appendTail(output);
    return output.toString();
}