Question

I was wondering if Java had an equivalent to C#’s named pattern matching. For example, in C# I can do something like this:

var pattern = @";(?<foo>\d{6});(?<bar>\d{6});";
var regex = new Regex(pattern , RegexOptions.None);
var match = regex.Match(";123456;123456;");

var foo = match.Groups["foo"].Success ? match.Groups["foo"].Value : null;
var bar = match.Groups["bar"].Success ? match.Groups["bar"].Value : null;

This just seems like a clean way to grab groups. Can Java do something similar, or do I need to grab groups based on index position?

String foo = matcher.group(0);

Answer 1

This is supported starting in Java 7. Your C# code can be translated to something like this:

String pattern = ";(?<foo>\\d{6});(?<bar>\\d{6});";
Pattern regex = Pattern.compile(pattern);
Matcher matcher = regex.matcher(";123456;123456;");
boolean success = matcher.find();

String foo = success ? matcher.group("foo") : null;
String bar = success ? matcher.group("bar") : null;

You have to create a Matcher object which doesn’t actually perform the regex test until you call find().

(I used find() because it can find a match anywhere in the input string, like the Regex.Match() method. The .matches() method only returns true if the regex matches the entire input string.)