How to make a regular expression looking for a list of extensions separated by a space

Question

Hello,

I want to be able to take a string of text from the user that should be formated like this:

.ext1 .ext2 .ext3 ...

Basically, I am looking for a dot, a string of alphanumeric characters of any length a space, and rinse and repeat. I am a little confused on how to say " i need a period, string of characters and a space". But also, the last extension could either be followed by nothing, or a space, or a series of spaces. Also, I guess in between extensions could be followed by any number of spaces?

EDIT: I made it clearer what I was looking for.

Thanks!

Answer 1

Try this:

^(?:\.[A-Za-z0-9]+ +)*\.[A-Za-z0-9]+ *$

(Rubular)

In a Java string literal you need to escape the backslashes:

"^(?:\\.[A-Za-z0-9]+ +)*\\.[A-Za-z0-9]+ *$"

Answer 2

(\.\w+)\s* Match this and get your results.
^((\.\w+)\s*)*$ Check this and if it's true, your String is exactly what you want.

For the last pattern thing, you can't (AFAIK) do both getting all extensions (separated) and checking that the last is followed by other things. Either you check your string, or you extract the extensions from it.

Answer 3

I'd start with something like: ^.[a-z0-9]+([\t\n\v ]+.[a-z0-9]+)*$