Regular expression question

[stuckonjava]

Produce a regular expression to describe each of the families of strings described below! Expression of time of the form “7.15am” or “11.34pm”

What I got was

(\d|\d\d) \. \d\d (am|pm)

But I'm not sure whether this is correct, could someone inform me if it is.

[Fubarable]

Produce a regular expression to describe each of the families of strings described below! Expression of time of the form “7.15am” or “11.34pm”

What I got was

(\d|\d\d) \. \d\d (am|pm)

But I'm not sure whether this is correct, could someone inform me if it is.

What happened when you put this in a small program and then threw a bunch of test Strings at it?

[stuckonjava]

What happened when you put this in a small program and then threw a bunch of test Strings at it?

I haven't learnt how to test them yet, I just wanted to get some practice in writing them fluently, is what I did correct?

[Fubarable]

It is one possible way to write this, but I think that you may have the cart before the horse -- read up on how to test your regexes before trying to create them, since your Java compiler is much quicker at answering these types of questions than a forum. Also look into using {1,2} notation for your first 1-2 character number rather than a group.

[stuckonjava]

It is one possible way to write this, but I think that you may have the cart before the horse -- read up on how to test your regexes before trying to create them, since your Java compiler is much quicker at answering these types of questions than a forum. Also look into using {1,2} notation for your first 1-2 character number rather than a group.

Thanks for your reply.

Could I just quickly ask what [01]?\d means for the first part of the time before the '.'

[Fubarable]

Thanks for your reply.

Could I just quickly ask what [01]?\d means for the first part of the time before the '.'

Have a look here: Regular Expressions Tutorial: repeat

The whole tutorial is excellent and one you should link to: Regular Expressions Tutorial

[stuckonjava]

I've read through it all now, thanks for the link.

There is however, one case which I'm findind difficult to get my head around.

The regular expression for any email address is:
\w(\.?[\w\-]+)*@\w+(\.[\w\-]+)+

Could anyone help break this down for me , thanks