Optional components in java regex

Question

I've been writing regex for long time and covering below scenarios by writing two regexes, since I do not know if there's a way to handle it by a single regex. So, I would like to hear if there's a way to write a single regex to capture the both at one shot.

Suppose that we have a standard starting with A and ending with Z, the field delimiter is a pipe | and each field consist of components delimited by a hat ^.

Input1: A|1|1^^3^4^5|loongText|Z
Input2: A|13|^2^|loongText|Z

The regex should give below output

Output1 : captured groups 1,,3,4,5
Output2 : captured groups ,2,,,

My attempt : A\|.\d*\|(.*)\^(.*)\^(.*)\^(.*)\^(.*?)\|.+?\|Z works for the first input but not the second.

What regex matches both inputs and gets the groups in correct order ?

[UPDATE] Group order is important. So group 1 should be 1, group 2 should be returning an empty and 2 in respectively for input 1 and input 2. Because based on the order they have different meanings in the standard.

Input3: A|13|1^2^3|loongText|Z
Expected output: {"group1" :1, "group2": 2, "group3": 3}, so having captures in the right group is also important.

If it were me, I'd extract the third field using a regex, then split it using split instead of trying to do something clever with captured groups. — RealSkeptic
– RealSkeptic, Commented Sep 18, 2022 at 15:49
Do you need the empty matches? Perhaps like this (?<=(?:^|\|)(?=\d*\^)[\d^]{0,100})\d+ regex101.com/r/mceSCT/1 Or using \G with a capture group like (?:(?:^|\|)(?=\d*\^)|\G(?!\A))\^*(\d+)\d* regex101.com/r/AEbupx/1 — The fourth bird
– The fourth bird, Commented Sep 18, 2022 at 16:07
@RealSkeptic this what I'm doing right now already. If the field is not complex split otherwise another regex. — Davut Gürbüz
– Davut Gürbüz, Commented Sep 18, 2022 at 16:14
And how can it become complex? Why another regex? Why aren't you showing us your actual solution? — RealSkeptic
– RealSkeptic, Commented Sep 18, 2022 at 16:40
@MikeM hope you don't mind I answer to it on behalf of you : ) But, even the split function take a regex input. It's inevitable. — Davut Gürbüz
– Davut Gürbüz, Commented Sep 18, 2022 at 19:02

Davut Gürbüz · Accepted Answer · 2022-09-18 18:59:55Z

1

I'm sharing this onbehalf of @MikeM, who answered originaly to this question.

A\|\d*\|(?:(\d*)\^?)?(?:(\d*)\^?)?(?:(\d*)\^?)?(?:(\d*)\^?)?(?:(\d*))\|.+?\|Z

This regex matches all 3 inputs in the right group order. Thanks.

answered Sep 18, 2022 at 18:59

Davut Gürbüz

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