Collect HashSet / Java 8 / Regex Pattern / Stream API

Question

Recently I change version of the JDK 8 instead 7 of my project and now I overwrite some code snippets using new features that came with Java 8.

final Matcher         


        

Answer 1

Marko's answer demonstrates how to get matches into a stream using a Spliterator. Well done, give that man a big +1! Seriously, make sure you upvote his answer before you even consider upvoting this one, since this one is entirely derivative of his.

I have only a small bit to add to Marko's answer, which is that instead of representing the matches as an array of strings (with each array element representing a match group), the matches are better represented as a MatchResult which is a type invented for this purpose. Thus the result would be a Stream instead of Stream. The code gets a little simpler, too. The tryAdvance code would be

    if (m.find()) {
        action.accept(m.toMatchResult());
        return true;
    } else {
        return false;
    }

The map call in his email-matching example would change to

    .map(mr -> mr.group(2))

and the OP's example would be rewritten as

Set set = matcherStream(mtr)
                      .map(mr -> mr.group(0).toLowerCase())
                      .collect(toSet());

Using MatchResult gives a bit more flexibility in that it also provides offsets of match groups within the string, which could be useful for certain applications.