Using java.util.regex.Pattern

Question

I´m not a programmer, so my level is newie in this field. I must create a regular expression to check two lines. Between these two lines A and B could be one, two or more different lines.

I´ve been reviewing link http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html but i´ve not reach the solution, althouth i think that i´m very close to the solution.

I am testing the expression ^(.*$) and this gets an entire line. If i write this expression twice it gets two lines. So it seems that this expression is getting as entire lines as occurrences of the expression.

But, i would like to check undetermined lines between A and B. I know that at least it will be one line If i write ^(.*$){1,} it doesn´t work.

Anyone knows which could be the mistake?

Thank you for your time Andres

Regexes is what you need.

Stanley Mungai
– Stanley Mungai

2013-04-24 10:49:05 +00:00
Commented Apr 24, 2013 at 10:49 — Stanley Mungai
– Stanley Mungai, Commented Apr 24, 2013 at 10:49

anubhava · Accepted Answer · 2013-04-24 10:56:45Z

1

DOT . in regex matches any character except newline character.

You're looking for DOTALL or s flag here that makes dot match any character including newline character as well. So if you want to match all the lines between literals A and B then use this regex:

(?s)A.*?B

(?s) is for DOTALL that will make .*? match all the characters including newline characters between A and B.

? is to make above regex non-greedy.

Read More: http://docs.oracle.com/javase/1.5.0/docs/api/java/util/regex/Pattern.html

answered Apr 24, 2013 at 10:56

anubhava

790k67 gold badges603 silver badges671 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

DeadlyJesus · Accepted Answer · 2013-04-24 10:52:26Z

0

Why don't you use Scanner ? It might be more related to what you want:

Scanner sc = new ...
while (sc.nextLine().compareTo(strB)!=0) {
whatYouWantToDo
}

answered Apr 24, 2013 at 10:52

DeadlyJesus

1,5632 gold badges12 silver badges26 bronze badges

1 Comment

Andriu Over a year ago

Hi, is it inside java.util.regex Class Pattern?. I think that "my" application that will check the pattern only understand regular expressions based on this java class.

Campfire · Accepted Answer · 2013-04-24 10:59:28Z

0

You could try to search for line terminators \r and \n. Depending on the source of the file you maybe have to experiment a bit. As far as I understood it, you want to match the lines, with at least one empty line in between? Try ^(.*)$\n{2,}^(.*)$

answered Apr 24, 2013 at 10:59

Campfire

9241 gold badge6 silver badges12 bronze badges

Comments

Joop Eggen · Accepted Answer · 2013-04-24 11:00:17Z

0

If you want to find two equal lines, using regex:

Pattern pattern = Pattern.compile("^(?:.*\n)*(.*\n)(?:.*\n)*\\1");
// Skip some lines, find a line, skip some lines, find the first group `(...)`
Matcher m = pattern.matcher(text);
while (m.find()) {
    System.out.println("Double: " + m.group(1);
}

The (?: ...) is a non-capturing group; that is, not available through m.group(#).

However this won't find line B in: "A\nB\nA\nB\n".

answered Apr 24, 2013 at 11:00

Joop Eggen

110k8 gold badges89 silver badges142 bronze badges

Collectives™ on Stack Overflow

Using java.util.regex.Pattern

4 Answers 4

Comments

1 Comment

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

1 Comment

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related