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Asked: 2026-05-26T14:30:32+00:00

I have a regex that contains a character class followed by TWO cadinality characters

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I have a regex that contains a character class followed by TWO “cadinality” characters – not sure what else they are called. If it matters the regex engine it’s running on is the built in java regex. The java string literal is:

"[a-zA-Z]{2}[ -]?+\\d{6}"

Or in non java land:

[a-zA-Z]{2}[ -]?+\d{6}

So specifically what does the [ -]?+ part mean? From testing as far as i can tell it’s like the + isn’t even there (originally I thought due to ‘order of operations’ that i wasn’t aware of perhaps it would get applied to everything in front of it like there were parenthesis there).

The following pass:

ab123456, ab-123456, ab 123456

The following fail:

aa--123456, aa  123456, aa - -123456, aa-aa-123456
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1 Answer

  1. Editorial Team

    It’s a possessive quantifier, essentially meaning that the ? will not give up its match for backtracking. It does not affect the number of repetitions that the ? will match – it will still be zero or one (greedy). The [ -] preceding it is simply a character class containing the space and hyphen characters.

    Other quantifier operators can also be made possessive by adding a + (i.e. *+ or ++ would be possessive versions of * and +, respectively).

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