Regex not required

Question

I am trying to develop a simple REGEX in Java with pattern like that :

@Pattern(regexp = "[a-zA-Z]{2}[0-9]{1}[2-8]{1}" , message = "The format is invalid")

but this message is still displayed when the field is empty, so i want to show this message only when the field is not empty (i want that the field is will be not required).

Thank you.

Do you mean either empty or that pattern by making it optional? `^(?:[a-zA-Z]{2}[0-9][2-8])?$` https://regex101.com/r/pKrWA1/1 — The fourth bird, Sep 23 '19 at 10:34
Hi. There's a syntax error in the snippet you've included. Also, you seem to be using some sort of a magic framework. Do at least mention its name somewhere (or a full path, with the package name, of the @Pattern annotation). There's just far too much missing from this question. — Richard the Spacecat, Sep 23 '19 at 10:34
Just curious, what are you trying to match with `[0-9]{1}[2-8]{1}`? — Toto, Sep 23 '19 at 11:54
Do not use `"[a-zA-Z]{2}[0-9]{1}[2-8]{1}|^$"`, it is the most inefficient approach. Use `^(?:[a-zA-Z]{2}[0-9][2-8])?$`. — Wiktor Stribiżew, Sep 23 '19 at 12:36

score 3 · Accepted Answer · answered Sep 23 '19 at 10:38

3

Try using the following regex, which matches both your expected string and empty string:

[a-zA-Z]{2}[0-9]{1}[2-8]{1}|^$

Java code:

@Pattern(regexp = "[a-zA-Z]{2}[0-9]{1}[2-8]{1}|^$", message = "The format is invalid")

answered Sep 23 '19 at 10:38

Tim Biegeleisen

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The fourth bird · Answer 2 · 2019-09-23T11:16:47.733

2

You could make your whole pattern optional using a non capturing group (?:...)?to match either an empty string or the whole pattern.

Note that you can omit the {1} part.

^(?:[a-zA-Z]{2}[0-9][2-8])?$

Regex demo

@Pattern(regexp = "^(?:[a-zA-Z]{2}[0-9][2-8])?$" , message = "The format is invalid")

edited Sep 23 '19 at 11:16

answered Sep 23 '19 at 11:00

The fourth bird

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Regex not required

2 Answers2