Java Regex to match a specific string or another specific string, or not at all?

Question

Imagine capturing the input with a regex:

2.1_3_4
3.2.1
3.2.1.RELEASE
3.2.1.SNAPSHOT

The numbers and the dots are easy enough to get

([0-9\._]+)

But how do you capture that plus "RELEASE" or "SNAPHOT" or none of those?

I played around with the or operator to no avail...

([0-9\._]+RELEASE||SNAPSHOT)  // no worky

btw, this is a nice regex tester: http://java-regex-tester.appspot.com/

Justin O Barber · Accepted Answer · 2013-02-12 05:24:12Z

5

I think you want this:

([0-9._]+(RELEASE|SNAPSHOT)?)

The (inside) parens form a group, and the question mark indicates the group may occur 0 or 1 times.

edited Feb 12, 2013 at 5:24

answered Feb 12, 2013 at 5:09

Justin O Barber

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3 Comments

pickypg Over a year ago

Probably (?:RELEASE|SNAPSHOT)? to avoid the inner match group.

Justin O Barber Over a year ago

@pickypg Yours would avoid matching the inner match group, but I think the op wants that group. Perhaps the op could clarify.

pickypg Over a year ago

Agreed, but based on his original attempt and 'plus "RELEASE" or "SNAPHOT"', I suspect he wants to basically ensure that it passes and get the whole thing. (Though it's worth noting that ...._RELEASE would match, which he might not expect)

Ali Shah Ahmed · Accepted Answer · 2013-02-12 05:22:14Z

1

You are doing great. You just need to make a few changes.
First, you do not use || for or, | is used. So RELEASE||SNAPSHOT would convert to RELEASE|SNAPSHOT.
Since release or snapshot is not mandatory, a ? should be placed after it. So the final regex becomes

([0-9\._]+(RELEASE|SNAPSHOT)?)

You can also use \d instead of 0-9. else than this, there is no need to escape . by \ when its present inside []
So finally, following could be the final regex

([\d._]+(RELEASE|SNAPSHOT)?)

answered Feb 12, 2013 at 5:22

Ali Shah Ahmed

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