Wanted: a very simple Java RegExp API

Question

I'm tired of writing

Pattern p = Pattern.compile(...
Matcher m = p.matcher(str);
if (m.find()) {
   ...

Over and over again in my code. I was going to write a helper class to make it neater, but I then I wondered: is there a library that tries to provide a simpler facade for Regular Expressions in Java?

I'm thinking something in the style of commons-lang and Guava.

CLARIFICATION: I am actually hoping for some general library that would make working with regular expression a more streamlined experience, kind of like how perl does it. The code above was just an example.

I was thinking of something I could use like this:

for (int question : RegEx.findAllInts("SO question #(\\d+)", str)) {
   // do something with int
}

Again, this is just an example of one of the many things I'd like to have. Probably not even a good example. APIs are hard.

UPDATE: I guess the answer is "No". Thanks for all the answers, have an upvote.

Answer 1

Since Java 1.4, you can also use String.matches(String regex). Which precisely is a facade to the aforementionned code.

Answer 2

Why not just write your own wrapper method? Sure, you should not reinvent the wheel but another library also means another dependency.

Answer 3

There is Jakarta Regexp (see the RE class). Have a look at this old thread for advantages of Jakarta's RegExp package over the Java built-in RegEx.

Answer 4

Pattern should only be compiled once; save it in a static final field. This at least saves you from repeating, at coding time an runtime, this step. That is to say, this step ought not always go hand-in-hand with creating a Matcher for performance reasons.

In your example, it seems RegEx plays the role of a Matcher object anyway. I hope it's not supposed to be a class with a static method since this would not work in a multithreaded environment -- the find and getInt calls are not connected then. So you need a Matcher of some sort anyway.

And so you're back to precisely the Java API, when design considerations are factored in. No I don't think there's a shorter way to do this correctly and efficiently.

Answer 5

There is a java library which has extend feature over the built-in java regex library . Have a look at RegExPlus. I haven't tried it personally.But hope this helps.

Answer 6

For the specific example you give, you might be able to improvise something using Guava's splitter:

for (String number : Splitter.onPattern("[^\d]+").split(input)) {
    // Do something with the number
}

or more specifically, if you had input like

SO question #1234, SO Question #3456, SO Question #5678

you might do

for (String number : Splitter.onPattern("(, )? SO Question #").split(input)) {
    // Do something
}

It's a bit hacky, but in specific cases it may do what you're after.

Answer 7

Yeah, it's always bugged me, too, having to write so much boilerplate to perform such common tasks. I think it would help a lot if String had a pair of methods like

public String findFirst(String regex)

public String[] findAll(String regex)

These represent the two most commonly performed regex operations that aren't already supported by String methods. If we had those, plus a dynamic replacement facility like Rewriter, we could almost forget about Pattern and Matcher. We would only need them when we're writing something really complicated, like a findAllInts() method. :D