Is there any difference practically between [a-zA-Z] and [a-z[A-Z]]?
According to java tutorial (and Pattern class javadoc):
[a-zA-Z] a through z, or A through Z, inclusive (range)
[a-d[m-p]] a through d, or m through p: [a-dm-p] (union)
Asked
Active
Viewed 1,481 times
2
Ilya Bystrov
- 2,902
- 2
- 14
- 21
-
2Range is `a-z`, union of ranges is `[a-zA-Z]` which in Java can also be written as `[a-z[A-Z]]` or `[[a-z][A-Z]]`. – Pshemo Nov 12 '14 at 22:08
-
3I suggest reading a better [article](http://www.rexegg.com/regex-class-operations.html#union), it is pretty thorough. – hwnd Nov 12 '14 at 22:11
1 Answers
2
Not much as far as I can see, other than making certain regexes easier to read. @hwnd's link to the regexx article gives good examples.
I've come up with a fairly esoteric use-case that might warrant it though: a character-class builder. You could build a character class by wrapping any number of other character classes in [] and you wouldn't have to worry about stripping [] from the various constituent classes.
Paul Hicks
- 13,289
- 5
- 51
- 78
-
1
-
1`[\p{Digit}[^5]]` is a union. It will end up matching everything. If you want to match digits except 5, you would have to use an intersection `[\p{Digit}&&[^5]]` – Misha Nov 12 '14 at 22:19
-
Good point. I shall wrack my brain to come up with a less-unuseful regex! – Paul Hicks Nov 12 '14 at 23:00