Properly using Regex in Java, Regex not matching

Question

I want to check if a string contains exactly 1 alphabetic char, that may or may not be preceded by any of ~, ! or ?. The expression I have set to match against is:

if (this.str.matches("[!~?]{1,9}?[a-z]{1}")) {

but when the input I have (this.str) is equal to 'p', this if block is not triggered. What am I doing wrong?

Some strings that should match:

!!~?p
p
~p
???!!?!??!~p

Thanks heaps :)

If the punctuation symbol (!, ~ and ?) can be optional (can be absent), use "[!~?]{0,9}[a-z]". Or even "[!~?]*[a-z]" where * means 0 or more occurrences. — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Nov 8, 2018 at 21:30
Would ~!???~~!!x be valid? If the "alphabetic char" can only preceded by 1 character, use "[!~?]?\\p{L}", where \\p{L} means any Unicode letter, not just a-z. — Andreas
– Andreas, Commented Nov 8, 2018 at 21:33
Please update your question with a set of strings that should and should not match for the desired outcome — Freiheit
– Freiheit, Commented Nov 8, 2018 at 21:34

Freiheit · Accepted Answer · 2018-11-08 21:33:45Z

1

I think you need [!~?]{0,9}?[a-z]. The issue was the {1,9} matches ~, !, or ? ONE to nine times. You state that its optional and therefore should be ZERO to nine times.

Try your regex out at https://regex101.com/r/m1ad8X/1.

Try @WiktorStribiżew correction at https://regex101.com/r/m1ad8X/2

And my solution at https://regex101.com/r/m1ad8X/3

answered Nov 8, 2018 at 21:33

Freiheit

8,8056 gold badges63 silver badges109 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Properly using Regex in Java, Regex not matching

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related