New help with Pattern in Java

2BOrNot2B · July 1st, 2008, 12:14 PM

Hi.

I am working with Pattern and Matcher in Java.
I need help creating a pattern to match the following strings:

    MAIL FROM:
    MAIL FM:
    MAIL FROM:

This is what I have on my pattern, "MAIL\\s+FR{0,1}O{0,1}M:"

My pattern seem to work if the string is "MAIL FRM:" or "MAIL FOM:", which is incorrect.

Please help.

Old Pedant · July 1st, 2008, 04:40 PM

Well, sure. The pattern

Code:

     "MAIL\\s+FR{0,1}O{0,1}M:"

says:

Code:

MAIL == literally
\\s+ == one or more spaces
F == literally
R{0,1} == an optional letter R
O{0,1} == an optional letter O
M: == literally

There are a couple of ways to solve this:

Code:

     "MAIL\\s+F(RO)?M:"

That makes the *group* RO optional. And that certainly works.

But my own preference would be K.I.S.S.

Code:

     "MAIL\\s+(FM|FROM)M:"

That says "FM" or "FROM" as choices.

p.s.: No reason to ever use {0,1} when ? means the same thing.