Get regular expression groups with Vavr

Question

Considering that Vavr provides tuples , is it possible to use them for capturing groups in regular expressions?

Taking an HTTP request line as an example string to match

GET /resource HTTP 1.1

and a matching pattern

Pattern.compile("(\\w+) (.+) (.+)")

are there methods in Vavr that return the three matched strings as a tuple?

Answer 1

It's easy to create this yourself:

/**
 * Gets the three matched groups of the {@code regex} from the {@code original}.
 *
 * @param regex    a {@link Pattern} that should have three groups in it and
                   match the {@code original}
 * @param original the string we'll match with the {@code regex}
 * @return a {@link Tuple3} of the three matched groups or {@link Option#none} if
 *         the {@code regex} did not match
 */
static Option<Tuple3<String, String, String>> getGroups3(Pattern regex,
                                                         CharSequence original) {
    var matcher = regex.matcher(original);
    return matcher.matches() && matcher.groupCount() == 3 ?
            Some(Tuple.of(matcher.group(1), matcher.group(2), matcher.group(3))) :
            Option.none();
}

This is how you could use the method:

var pattern = Pattern.compile("(\\w+) (.+) (.+)");
var requestLine = "GET /resource HTTP 1.1";

var result = getGroups3(pattern, requestLine).fold(
        // No match
        () -> String.format("Could not parse request method, resource, and " +
                        "HTTP version from request line. Request line is '%s'",
                requestLine),
        // Do whatever you want with the three matched strings
        tuple3 -> tuple3.apply((method, resource, httpVersion) ->
                String.format("Method is %s, resource is %s, HTTP version is %s",
                        method, resource, httpVersion)));