RegEx problem

[Soeren Meyer-Eppler]

Hello,

I have a very frustrating problem getting Javas regexes to run. I have
no idea what I'm doing wrong, since even the most trivial expressions
don't find any matches - even when I've tested and verified them in
other regex enabled tools like UltraEdit or so.

The simplest test I could think of is the following:

public static void main(String[] args)
{
Pattern pattern = Pattern.compile( ".*" );
Matcher matcher = pattern.matcher( "hello" );
System.out.println( matcher.group());
}

which gives me:

Exception in thread "main" java.lang.IllegalStateException: No match found
at java.util.regex.Matcher.group(Unknown Source)
at java.util.regex.Matcher.group(Unknown Source)
at BinNavi.GraphNavigator.main(GraphNavigator.java:1688)

WTF?! I mean shouldn't .* match just about anything? Including the empty
string? Similarly, matching "hello" to "hello" doesn't work, "t" to
"t"... Am I using it wrong?

I'm running on Java Version 1.5.0 (Build 1.5.0_06-b05), jdk1.5.0, my
test environment is Eclipse.

I'd appreciate any hints, since I'm sure this is a stupid mistake on my
part.

regards,

Sören Meyer-Eppler

 

[Soeren Meyer-Eppler]

.... argh. Solved the problem. Of course I forgot to call matcher.find().
Although I'm not quite sure why it's necessary since it already knows
the search subject string and could search on construction.

Ah well, sorry about that,

Sören

 

[Jean-Francois Briere]

Although I'm not quite sure why it's necessary

Because you can do other things than find() with a matcher.
So you have to specify to the matcher what you need to do.

Regards

 

[Roedy Green]

I have a very frustrating problem getting Javas regexes to run. I have
no idea what I'm doing wrong, since even the most trivial expressions
don't find any matches - even when I've tested and verified them in
other regex enabled tools like UltraEdit or so.

see some tricks at http://mindprod.com/jgloss/regex.html

 

[Guest]

since group. ==> ".*" should be "(.*)"

 

[Robert Klemme]

... argh. Solved the problem. Of course I forgot to call
matcher.find(). Although I'm not quite sure why it's necessary since
it already knows the search subject string and could search on
construction.

1. because there's also matches() as Jean pointed out.

2. you can invoke find multiple times

Kind regards

robert