CODEWITHSUNDEEP
javaregexregex-lookarounds
Viktor
Viktor

Reputation: 33

How to create regex with multiple conditions

I need to scan log file to find some substrings.

How to combine conditions below in single regex expression:

I tried something like (?!DDD|EEE|FFF)(AAA|BBB|CCC) but was not successful.

Regular expression syntax should be supported by the Java Pattern class.

Thank you!

Upvotes: 2

Views: 516

Answers (1)

jwismar
jwismar

Reputation: 12268

I came up with this one:

(?!.*?(DDD|EEE|FFF).*?)(?<!(DDD|EEE|FFF))(AAA|BBB|CCC)

It seems to work, using these test cases:

123AAA //matches
123BBB //matches
123CCC //matches
123DDD //no match
123EEE //no match
123FFF //no match
AAADDD //no match
EEEBBB //no match

Explanation: Don't match if there's "DDD", "EEE", or "FFF" anywhere in the string.

Don't match if there was a "DDD", "EEE", or "FFF" before the matching substring. (I don't know why this is needed. If I leave it out, "EEEBBB" gets a match, and I think it shouldn't. I need to figure this out.)

Update: I think I needed the negative lookbehind because I wasn't considering the context of where the substring match occurred within the line.

Here's a version that doesn't require the negative lookbehind:

(?!^.*?(DDD|EEE|FFF).*?$)(?:^.*?(AAA|BBB|CCC).*?$)

Seems to work because I'm considering the whole line.

Another update. (Can't leave it alone.) This is optimized a bit:

(?!^.*?(?:DDD|EEE|FFF).*$)^.*?(AAA|BBB|CCC).*$

Upvotes: 1

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