Java Pattern Matching - groupcount

quinnd6

Im trying to figure out how to use patterns and matcher.

I don't understand how groupCount works.

How does it work?

Are there any good explanations about?

Farouk.Bulsara

quinnd6 wrote:

Im trying to figure out how to use patterns and matcher.

I don't understand how groupCount works.

How does it work?

Are there any good explanations about?

http://java.sun.com/j2se/1.4.2/docs/api/java/util/regex/Matcher.html#groupCount()

Evil Phil

Google?

sicruise

Are we not supposed to be an alternative to google?

ressem

How about
http://java.sun.com/docs/books/tutorial/essential/regex/intro.html

Do you understand what groups are, in the context of Matcher etc.

Take a configuration file with a line that looks like:
clients: 192.168.1.50
192.168.200.52 MyComputer optional description
10.168.7.63

amongst other stuff. And you want to retrieve these ip addresses.
You might write a regex like
String clientregex =
"^clients:\D*
(
(\d{1,3}\\.\d{1,3}\\.\d{1,3}\\.\d{1,3})
(.*?)??$)
){1,}?"

2nd and 5th deal with allowing multiple addresses
3nd line is the ip address.
4rd line is the description

Above not guaranteed to work as it's a friday but anyways.
Each ( ...stuff.... ) Creates a group.

So above there's
group 0 which will match the entire expression being tested. Not included in count
group 1 should match the first ip + description (if it existed).
group 2 should match the first ip
if there was a description then this would be group 3, but there isn't so group 3 is the second ip + description.
group 4 is the second ip
group 5 is the second ip's description
group 6 is the third ip + description
group 7 is the third ip

so groupcount will equal 7 with this data.

So it can be used to iterate between the above values like.
for (int i=1; i<mymatcher.groupcount(); i++)
{ value= mymatcher.group(i);}