Set RegEx in Java to be non-greedy by default

Question

I have Strings like the following:

"parameter: param0=true, param1=401230 param2=asset client: desktop"
"parameter: param0=false, param1=15230 user: user213 client: desktop"
"parameter: param0=false, param1=51235 param2=asset result: ERROR"

The pattern is parameter:, then the param's, and after the params either client: and/or user: and/or result.

I want to match the stuff between parameter: and the first occurrence of either client:, user: or result:

So for the 2nd String it should match param0=false, param1=15230.

My regex is:

parameter:\s+(.*)\s+(result|client|user):

But now if I match the 2nd String it captures param0=false, param1=15230 user: user213 (looks like regex is matching greedy)

How to fix this? parameter:\s+(.*)\s+(result|client|user)+?: won't fix it
With this regex tester I can add the modifier U to the regex to make regex lazy by default, is this possible in Java too?

You can use `U` flag to use ungreedy or just concatenate `?` to your `*` and having `x*?` or `x+?` — Federico Piazza, Aug 14 '14 at 16:09
@Unihedron oh good to know. There are so many engines and some many different features that I mess up. Thanks. — Federico Piazza, Aug 14 '14 at 16:29
@Fede I posted a link to the Java Pattern documentation in my answer. You can also see [Reference - What does this regex mean?](http://stackoverflow.com/questions/22937618/reference-what-does-this-regex-mean) — Unihedron, Aug 14 '14 at 16:30

score 5 · Accepted Answer · answered Aug 14 '14 at 16:03

5

Try putting the ? character inside the first captured group (the subpattern you intend to extract):

parameter:\\s+(.*?)\\s+(result|client|user):

answered Aug 14 '14 at 16:03

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score 5 · Answer 2 · answered Aug 14 '14 at 16:06

No. There is no ungreedy modifier in Java. You have to use ? behind modifiers to make the quantifiers as lazy capture.

This means you should denote all quantifiers with a ?, see the following pattern:

"parameter:\\s+?(.*?)\\s+?(result|client|user):"

Specified by:
http://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Set RegEx in Java to be non-greedy by default

2 Answers2