Question

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]+ *$"