ct2602
Reputation: 95
How to reject repetition of character within Java regular expression
I am looking for help with a Java regular expression please.
My regular expression should accept a string of length 5 only, with characters matching [BDILMOP] only.
No repeated characters are allowed - eg. BDILM is allowed, but BDILL or BDLLL are not.
Please help - I'm new to regex and so would appreciate any advice that you could throw my way.
Thanks!
Upvotes: 0
Views: 375
Answers (1)
anubhava
Reputation: 784998
You can use this negative lookahead based regex:
^(?!.*(.).*\1)[BDILMOP]{5}$
(?!.*(.).*\1) is negative lookahead which fails the match if there is any repetition in input. (.) captures a letter in group #1 and \1 is back-reference of the same group thus checking repetition.
Upvotes: 1
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