CODEWITHSUNDEEP
javaregex
Nikša Baldun
Nikša Baldun

Reputation: 1894

Java regex - can't start or end with slash or space, and no consecutive slashes

I need a regex with the following requirements:

I have the following so far:

^[A-Za-z0-9][A-Za-z0-9/ ]{0,18}[A-Za-z0-9]$

I think it covers everything except consecutive slashes. Is there a way to meet this requirement in Java regex?

Upvotes: 2

Views: 894

Answers (1)

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 627488

You can add that condition using a lookahead at the beginning:

^(?!.*//)[A-Za-z0-9][A-Za-z0-9/ ]{0,18}[A-Za-z0-9]$
 ^^^^^^^^

See the regex demo

The lookahead (?!.*//) is negative due to (?! and is failing the match once it finds any // after any 0+ characters other than a newline (.*).

You may use it without ^ and $ with String#matches (see demo):

String input = "abc //abc";
if (!input.matches("(?!.*//)[A-Za-z0-9][A-Za-z0-9/ ]{0,18}[A-Za-z0-9]")) { 
        System.out.println("Not matching!");    
}

as String#matches requires a full string match, but I'd keep the anchors explicit for clarity.

Upvotes: 5

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