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Java Matcher matches() method to match the entire region against the pattern

I have a pattern (\{!(.*?)\})+ that can be used to validate an expression of format {!someExpression} one or more number of times.
I am performing
Pattern.compile("(\\{!(.*?)\\})+").matcher("{!expression1} {!expression2}").matches() to match the entire region against the pattern.
There is a space between expression1 and expression2.
Expected -> false
Actual -> true
I tried both greedy and lazy quantifiers but not able to figure out the catch here. Any help is appreciated.

Of course it matches. Your regexp says so. matches() matches the whole string, so you're doing exactly what you are asking. The point is, that regex matches the whole string. Try it in any regex tool.
Specifically, (.*?) will happily match expression1} {!expression2. Why shouldn't it? You said 'non-greedy' which doesn't do anything unless we're talking about subgroup matching; non-greediness cannot change what is being matched, it only affects, if it matches, how the groups are divided out. Non-greedy does not mean 'magically do what I want you to', however useful that might seem to be. . will match } just as well as x.
As a general rule if you're using non-greediness you're doing it wrong. It's not a universal rule; if you really know what you're doing (mostly: That you're modifying how backrefs / group matches / find() ends up spacing it out), it's fine. If you're tossing non-greediness in there as you write your regexp that's usually a sign you misunderstand what you're actually writing down.
Presumably, your intent with the non-greedy operator here is that you do not want it to also consume the } that 'ends' the {!expr} block.
In which case, just ask for that then: "Consume everything that isn't a }":
Pattern.compile("(\\{!([^}]*)\\})+").matcher("{!expression1} {!expression2}").matches()
works great.
If your intent is instead that expressions can also contain {} symbols and that this is a much more convoluted grammar system then your question cannot be answered without a full breakdown of what the grammarsystem entails. Note that many grammars are not 'regular' (that's a specific term that refers to a subset of all imaginable grammars), then it cannot be parsed out with a regular expression. That's what the 'regular' in regular expression refers to: A class of grammars. regexes can be used meaningfully on anything that fits a regular grammar. They are useless for anything that isn't, even if it seems like it could work. Thus, if there is a sizable grammar behind this {expr} syntax, it's possible you need an actual full parser for it.
As a simple example, java the language is not regular and therefore cannot meaningfully be parsed with regexes (that is: Whatever aim your regex has, I can write a valid java file that the compiler understands which your regex won't).

understanding regex if then statements

So I'm not sure if I understand how this works and would like
a simple explanation to how they work is all. I probably have it way off. A pure regex solution is required, and I don't know if this is possible. If it is, a solution would be awesome too, but a shove in the right direction would be good for my learning process ^_^
This is how I thought the if/then/else option built into my regex engines was formatted:
?(condition)if regex|else regex
I want it to capture a string from a very specific location only when this string exists within a certain section of javascript. Because this is how I thought it worked after a decent amount of research I tried out a few variations of this code but they all ended up something like this.
((?^view_large$)Tables-137(.*?)search.htm)
Also of relevance: I'm using an java based app that has regex searches which pull the data I need so I cannot write an if statement in java which would be my preferred method. It's a pain to have to do it this way, but at the moment I have no other choice. I'm trying really hard for them to allow java code functionality instead of pure regex for more versatile options.
So to summarize, is there even a if/then option in regex and if so how is it formatted for what I'm trying to accomplish?
EDIT: The string that I want to be the "if condition" is like this: if view_large string exists and is not null then capture the exact string 500/ which is captured within the catch all group I used: (.*?)

There is no conditionals in Java regexp, but you can simulate them by writing two expressions that include mutually exclusive look-behind constructs, like this:
((?<=if )then)|((?<!if )end)
This expression will match "then" when it is preceded by an "if "; it will match "end" when it is not preceded by an "if "

The Javadoc for java.util.regex.Pattern mentions, in its list of "Perl constructs not supported by this class":
The conditional constructs (?(condition)X) and (?(condition)X|Y).
So, no dice. But you should look through the Javadoc to see if you can achieve what you need by using regex features that it does support. (Or, if you post some more detailed examples, we can try to help.)

Try lookaround assertions.
For example, say you want to capture FOOBAR only if there is a 4+ digit number somewhere:
(?=.*\d{4}).*(FOOBAR)

How to add features missing from the Java regex implementation?

I'm new to Java. As a .Net developer, I'm very much used to the Regex class in .Net. The Java implementation of Regex (Regular Expressions) is not bad but it's missing some key features.
I wanted to create my own helper class for Java but I thought maybe there is already one available. So is there any free and easy-to-use product available for Regex in Java or should I create one myself?
If I would write my own class, where do you think I should share it for the others to use it?
[Edit]
There were complaints that I wasn't addressing the problem with the current Regex class. I'll try to clarify my question.
In .Net the usage of a regular expression is easier than in Java. Since both languages are object oriented and very similar in many aspects, I expect to have a similar experience with using regex in both languages. Unfortunately that's not the case.
Here's a little code compared in Java and C#. The first is C# and the second is Java:
In C#:
string source = "The colour of my bag matches the color of my shirt!";
string pattern = "colou?r";
foreach(Match match in Regex.Matches(source, pattern))
{
Console.WriteLine(match.Value);
}
In Java:
String source = "The colour of my bag matches the color of my shirt!";
String pattern = "colou?r";
Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(source);
while(m.find())
{
System.out.println(source.substring(m.start(), m.end()));
}
I tried to be fair to both languages in the sample code above.
The first thing you notice here is the .Value member of the Match class (compared to using .start() and .end() in Java).
Why should I create two objects when I can call a static function like Regex.Matches or Regex.Match, etc.?
In more advanced usages, the difference shows itself much more. Look at the method Groups, dictionary length, Capture, Index, Length, Success, etc. These are all very necessary features that in my opinion should be available for Java too.
Of course all of these features can be manually added by a custom proxy (helper) class. This is main reason why I asked this question. We don't have the breeze of Regex in Perl but at least we can use the .Net approach to Regex which I think is very cleverly designed.

From your edited example, I can now see what you would like. And you have my sympathies in this, too. Java’s regexes are a long, long, long ways from the convenience you find in Ruby or Perl. And they pretty much always will be; this cannot be fixed, so we’re stuck with this mess forever — at least in Java. Other JVM languages do a better job at this, especially Groovy. But they still suffer some of the inherent flaws, and can only go so far.
Where to begin? There are the so-called convenience methods of the String class: matches, replaceAll, replaceFirst, and split. These can sometimes be ok in small programs, depending how you use them. However, they do indeed have several problems, which it appears you have discovered. Here’s a partial list of those problems, and what can and cannot be done about them.
The inconvenience method is very bizarrely named “matches” but it requires you to pad your regex on both sides to match the entire string. This counter-intuitive sense is contrary to any sense of the word match as used in any previous language, and constantly bites people. Patterns passed into the other 3 inconvenience methods work very unlike this one, because in the other 3, they work like normal patterns work everywhere else; just not in matches. This means you can’t just copy your patterns around, even within methods in the same darned class for goodness’ sake! And there is no find convenience method to do what every other matcher in the world does. The matches method should have been called something like FullMatch, and there should have been a PartialMatch or find method added to the String class.
There is no API that allows you to pass in Pattern.compile flags along with the strings you use for the 4 pattern-related convenience methods of the String class. That means you have to rely on string versions like (?i) and (?x), but those do not exist for all possible Pattern compilation flags. This is highly inconvenient to say the least.
The split method does not return the same result in edge cases as split returns in the languages that Java borrowed split from. This is a sneaky little gotcha. How many elements do you think you should get back in the return list if you split the empty string, eh? Java manufacturers a fake return element where there should be one, which means you can’t distinguish between legit results and bogus ones. It is a serious design flaw that splitting on a ":", you cannot tell the difference between inputs of "" vs of ":". Aw, gee! Don’t people ever test this stuff? And again, the broken and fundamentally unreliable behavior is unfixable: you must never change things, even broken things. It’s not ok to break broken things in Java the wayt it is anywhere else. Broken is forever here.
The backslash notation of regexes conflicts with the backslash notation used in strings. This makes it superduper awkward, and error-prone, too, because you have to constantly add lots of backslashes to everything, and it’s too easy to forget one and get neither warning nor success. Simple patterns like \b\w+\b become nightmares in typographical excess: "\\b\\w+\\b". Good luck with reading that. Some people use a slash-inverter function on their patterns so that they can write that as "/b/w+/b" instead. Other than reading in your patterns from a string, there is no way to construct your pattern in a WYSIWYG literal fashion; it’s always heavy-laden with backslashes. Did you get them all, and enough, and in the right places? If so, it makes it really really hard to read. If it isn’t, you probably haven’t gotten them all. At least JVM languages like Groovy have figured out the right answer here: give people 1st-class regexes so you don’t go nuts. Here’s a fair collection of Groovy regex examples showing how simple it can and should be.
The (?x) mode is deeply flawed. It doesn’t take comments in the Java style of // COMMENT but rather in the shell style of # COMMENT. It doesn’t work with multiline strings. It doesn’t accept literals as literals, forcing the backslash problems listed above, which fundamentally compromises any attempt at lining things up, like having all comments begin on the same column. Because of the backslashes, you either make them begin on the same column in the source code string and screw them up if you print them out, or vice versa. So much for legibility!
It is incredibly difficult — and indeed, fundamentally unfixably broken — to enter Unicode characters in a regex. There is no support for symbolically named characters like \N{QUOTATION MARK}, \N{LATIN SMALL LETTER E WITH GRAVE}, or \N{MATHEMATICAL BOLD CAPITAL C}. That means you’re stuck with unmaintainable magic numbers. And you cannot even enter them by code point, either. You cannot use \u0022 for the first one because the Java preprocessor makes that a syntax error. So then you move to \\u0022 instead, which works until you get to the next one, \\u00E8, which cannot be entered that way or it will break the CANON_EQ flag. And the last one is a pure nightmare: its code point is U+1D402, but Java does not support the full Unicode set using their code point numbers in regexes, forcing you to get out your calculator to figure out that that is \uD835\uDC02 or \\uD835\\uDC02 (but not \\uD835\uDC02), madly enough. But you cannot use those in character classes due to a design bug, making it impossible to match say, [\N{MATHEMATICAL BOLD CAPITAL A}-\N{MATHEMATICAL BOLD CAPITAL Z}] because the regex compiler screws up on the UTF-16. Again, this can never be fixed or it will change old programs. You cannot even get around the bug by using the normal workaround to Java’s Unicode-in-source-code troubles by compiling with java -encoding UTF-8, because the stupid thing stores the strings as nasty UTF-16, which necessarily breaks them in character classes. OOPS!
Many of the regex things we’ve come to rely on in other languages are missing from Java. There are no named groups for examples, nor even relatively-numbered ones. This makes constructing larger patterns out of smaller ones fundamentally error prone. There is a front-end library that allows you to have simple named groups, and indeed this will finally arrive in production JDK7. But even so there is no mechanism for what to do with more than one group by the same name. And you still don’t have relatively numbered buffers, either. We’re back to the Bad Old Days again, stuff that was solved aeons ago.
There is no support a linebreak sequence, which is one of the only two “Strongly Recommended” parts of the standard, which suggests that \R be used for such. This is awkward to emulate because of its variable-length nature and Java’s lack of support for graphemes.
The character class escapes do not work on Java’s native character set! Yes, that’s right: routine stuff like \w and \s (or rather, "\\w" and "\\b") does not work on Unicode in Java! This is not the cool sort of retro. To make matters worse, Java’s \b (make that "\\b", which isn’t the same as "\b") does have some Unicode sensibility, although not what the standard says it must have. So for example a string like "élève" will never in Java match the pattern \b\w+\b, and not merely in entirety per Pattern.matches, but indeed at no point whatsoever as you might get from Pattern.find. This is just so screwed up as to beggar belief. They’ve broken the inherent connection between \w and \b, then misdefined them to boot!! It doesn’t even know what Unicode Alphabetic code points are. This is supremely broken, and they can never fix it because that would change the behavior of existing code, which is strictly forbidden in the Java Universe. The best you can do is create a rewrite library that acts as a front end before it gets to the compile phase; that way you can forcibly migrate your patterns from the 1960s into the 21st century of text processing.
The only two Unicode properties supported are the General Categories and the Block properties. The general category properties only support the abbreviations like \p{Sk}, contrary to the standards Strong Recommendation to also allow \p{Modifier Symbol}, \p{Modifier_Symbol}, etc. You don’t even get the required aliases the standard says you should. That makes your code even more unreadable and unmaintainable. You will finally get support for the Script property in production JDK7, but that is still seriously short of the mininum set of 11 essential properties that the Standard says you must provide for even the minimal level of Unicode support.
Some of the meagre properties that Java does provide are faux amis: they have the same names as official Unicode propoperty names, but they do something altogether different. For example, Unicode requires that \p{alpha} be the same as \p{Alphabetic}, but Java makes it the archaic and no-longer-quaint 7-bit alphabetics only, which is more than 4 orders of magnitude too few. Whitespace is another flaw, since you use the Java version that masquerades as Unicode whitespace, your UTF-8 parsers will break because of their NO-BREAK SPACE code points, which Unicode normatively requires be deemed whitespace, but Java ignores that requirement, so breaks your parser.
There is no support for graphemes, the way \X normally provides. That renders impossible innumerably many common tasks that you need and want to do with regexes. Not only are extended grapheme clusters out of your reach, because Java supports almost none of the Unicode properties, you cannot even approximate the old legacy grapheme clusters using the standard (?:\p{Grapheme_Base}\p{Grapheme_Extend}]*). Not being able to work with graphemes makes even the simplest sorts of Unicode text processing impossible. For example, you cannot match a vowel irrespective of diacritic in Java. The way you do this in a language with grapheme supports varies, but at the very least you should be able to throw the thing into NFD and match (?:(?=[aeiou])\X). In Java, you cannot do even that much: graphemes are beyond your reach. And that means Java cannot even handle its own native character set. It gives you Unicode and then makes it impossible to work with it.
The convenience methods in the String class do not cache the compiled regex. In fact, there is no such thing as a compile-time pattern that gets syntax-checked at compile time — which is when syntax checking is supposed to occur. That means your program, which uses nothing but constant regexes fully understood at compile time, will bomb out with an exception in the middle of its run if you forget a little backslash here or there as one is wont to do due to the flaws previously discussed. Even Groovy gets this part right. Regexes are far too high-level a construct to be dealt with by Java’s unpleasant after-the-fact, bolted-on-the-side model — and they are far too important to routine text processing to be ignored. Java is much too low-level a language for this stuff, and it fails to provide the simple mechanics out of which might yourself build what you need: you can’t get there from here.
The String and Pattern classes are marked final in Java. That completely kills any possibility of using proper OO design to extend those classes. You can’t create a better version of a matches method by subclassing and replacement. Heck, you can’t even subclass! Final is not a solution; final is a death sentence from which there is no appeal.
Finally, to show you just how brain-damaged Java’s truly regexes are, consider this multiline pattern, which shows many of the flaws already described:
String rx =
"(?= ^ \\p{Lu} [_\\pL\\pM\\d\\-] + \$)\n"
+ " # next is a big can't-have set \n"
+ "(?! ^ .* \n"
+ " (?: ^ \\d+ $ \n"
+ " | ^ \\p{Lu} - \\p{Lu} $ \n"
+ " | Invitrogen \n"
+ " | Clontech \n"
+ " | L-L-X-X # dashes ok \n"
+ " | Sarstedt \n"
+ " | Roche \n"
+ " | Beckman \n"
+ " | Bayer \n"
+ " ) # end alternatives \n"
+ " \\b # only on a word boundary \n"
+ ") # end negated lookahead \n"
;
Do you see how unnatural that is? You have to put literal newlines in your strings; you have to use non-Java comments; you cannot make anything line up because of the extra backslashes; you have to use definitions of things that don’t work right on Unicode. There are many more problems beyond that.
Not only are there no plans to fix almost any of these grievous flaws, it is indeed impossible to fix almost any of them at all, because you change old programs. Even the normal tools of OO design are forbidden to you because it’s all locked down with the finality of a death sentence, and it cannot be fixed.
So Alireza Noori, if you feel Java’s clumsy regexes are too hosed for reliable and convenient regex processing ever to be possible in Java, I cannot gainsay you. Sorry, but that’s just the way it is.
“Fixed in the Next Release!”
Just because some things can never be fixed does not mean that nothing can ever be fixed. It just has to be done very carefully. Here are the things I know of which are already fixed in current JDK7 or proposed JDK8 builds:
The Unicode Script property is now supported. You may use any of the equivalent forms \p{Script=Greek}, \p{sc=Greek}, \p{IsGreek}, or \p{Greek}. This is inherently superior to the old clunky block properties. It means you can do things like [\p{Latin}\p{Common}\p{Inherited}], which is quite important.
The UTF-16 bug has a workaround. You may now specify any Unicode code point by its number using the \x{⋯} notation, such as \x{1D402}. This works even inside character classes, finally allowing [\x{1D400}-\x{1D419}] to work properly. You still must double backslash it though, and it only works in regexex, not strings in general as it really ought to.
Named groups are now supported via the standard notation (?<NAME>⋯) to create it and \k<NAME> to backreference it. These still contribute to numeric group numbers, too. However, you cannot get at more than one of them in the same pattern, nor can you use them for recursion.
A new Pattern compile flag, Pattern.UNICODE_CHARACTER_CLASSES and associated embeddable switch, (?U), will now swap around all the definitions of things like \w, \b, \p{alpha}, and \p{punct}, so that they now conform to the definitions of those things required by The Unicode Standard.
The missing or misdefined binary properties \p{IsLowercase}, \p{IsUppercase}, and \p{IsAlphabetic} will now be supported, and these correspond to methods in the Character class. This is important because Unicode makes a significant and pervasive distinction between mere letters and cased or alphabetic code points. These key properties are among those 11 essential properties that are absolutely required for Level 1 compliance with UTS#18, “Unicode Regular Expresions”, without which you really cannot work with Unicode.
These enhancements and fixes are very important to finally have, and so I am glad, even excited, to have them.
But for industrial-strength, state-of-the-art regex and/or Unicode work, I will not be using Java. There’s just too much missing from Java’s still-patchy-after-20-years Unicode model to get real work done if you dare to use the character set that Java gives. And the bolted-on-the-side model never works, which is all Java regexes are. You have to start over from first principles, the way Groovy did.
Sure, it might work for very limited applications whose small customer base is limited to English-language monoglots rural Iowa with no external interactions or any need for characters beyond what an old-style telegraph could send. But for how many projects is that really true? Fewer even that you think, it turns out.
It is for this reason that a certain (and obvious) multi-billion-dollar just recently cancelled international deployment of an important application. Java’s Unicode support — not just in regexes, but throughout — proved to be too weak for the needed internationalization to be done reliably in Java. Because of this, they have been forced to scale back from their originally planned wordwide deployment to a merely U.S. deployment. It’s positively parochial. And no, there are Nᴏᴛ Hᴀᴘᴘʏ; would you be?
Java has had 20 years to get it right, and they demonstrably have not done so thus far, so I wouldn’t hold my breath. Or throw good money after bad; the lesson here is to ignore the hype and instead apply due diligence to make very sure that all the necessary infrastructure support is there before you invest too much. Otherwise you too may get stuck without any real options once you’re too far into it to rescue your project.
Caveat Emptor

One can rant, or one can simply write:
public class Regex {
/**
* #param source
* the string to scan
* #param pattern
* the regular expression to scan for
* #return the matched
*/
public static Iterable<String> matches(final String source, final String pattern) {
final Pattern p = Pattern.compile(pattern);
final Matcher m = p.matcher(source);
return new Iterable<String>() {
#Override
public Iterator<String> iterator() {
return new Iterator<String>() {
#Override
public boolean hasNext() {
return m.find();
}
#Override
public String next() {
return source.substring(m.start(), m.end());
}
#Override
public void remove() {
throw new UnsupportedOperationException();
}
};
}
};
}
}
Used as you wish:
public class RegexTest {
#Test
public void test() {
String source = "The colour of my bag matches the color of my shirt!";
String pattern = "colou?r";
for (String match : Regex.matches(source, pattern)) {
System.out.println(match);
}
}
}

Some of the API flaws mentioned in #tchrist's answer were fixed in Kotlin.

Boy, do I hear you on that one Alireza! Regex's are confusing enough without there being so many syntax variations amonng them. I too do a lot more C# than Java programming and had the same issue.
I found this to be very helpful:
http://www.tusker.org/regex/regex_benchmark.html
- it's a list of alternative regular expression implementations for Java, benchmarked.

This one is darned good, if I do say so myself!
regex-tester-tool

When would it be worth using RegEx in Java?

I'm writing a small app that reads some input and do something based on that input.
Currently I'm looking for a line that ends with, say, "magic", I would use String's endsWith method. It's pretty clear to whoever reads my code what's going on.
Another way to do it is create a Pattern and try to match a line that ends with "magic". This is also clear, but I personally think this is an overkill because the pattern I'm looking for is not complex at all.
When do you think it's worth using RegEx Java? If it's complexity, how would you personally define what's complex enough?
Also, are there times when using Patterns are actually faster than string manipulation?
EDIT: I'm using Java 6.

Basically: if there is a non-regex operation that does what you want in one step, always go for that.
This is not so much about performance, but about a) readability and b) compile-time-safety. Specialized non-regex versions are usually a lot easier to read than regex-versions. And a typo in one of these specialized methods will not compile, while a typo in a Regex will fail miserably at runtime.
Comparing Regex-based solutions to non-Regex-bases solutions
String s = "Magic_Carpet_Ride";
s.startsWith("Magic"); // non-regex
s.matches("Magic.*"); // regex
s.contains("Carpet"); // non-regex
s.matches(".*Carpet.*"); // regex
s.endsWith("Ride"); // non-regex
s.matches(".*Ride"); // regex
In all these cases it's a No-brainer: use the non-regex version.
But when things get a bit more complicated, it depends. I guess I'd still stick with non-regex in the following case, but many wouldn't:
// Test whether a string ends with "magic" in any case,
// followed by optional white space
s.toLowerCase().trim().endsWith("magic"); // non-regex, 3 calls
s.matches(".*(?i:magic)\\s*"); // regex, 1 call, but ugly
And in response to RegexesCanCertainlyBeEasierToReadThanMultipleFunctionCallsToDoTheSameThing:
I still think the non-regex version is more readable, but I would write it like this:
s.toLowerCase()
.trim()
.endsWith("magic");
Makes the whole difference, doesn't it?

You would use Regex when the normal manipulations on the String class are not enough to elegantly get what you need from the String.
A good indicator that this is the case is when you start splitting, then splitting those results, then splitting those results. The code is getting unwieldy. Two lines of Pattern/Regex code can clean this up, neatly wrapped in a method that is unit tested....

Anything that can be done with regex can also be hand-coded.
Use regex if:
Doing it manually is going to take more effort without much benefit.
You can easily come up with a regex for your task.
Don't use regex if:
It's very easy to do it otherwise, as in your example.
The string you're parsing does not lend itself to regex. (it is customary to link to this question)

I think you are best with using endsWith. Unless your requirements change, it's simpler and easier to understand. Might perform faster too.
If there was a bit more complexity, such as you wanted to match "magic", "majik', but not "Magic" or "Majik"; or you wanted to match "magic" followed by a space and then 1 word such as "... magic spoon" but not "...magic soup spoon", then I think RegEx would be a better way to go.

Any complex parsing where you are generating a lot of Objects would be better done with RegEx when you factor in both computing power, and brainpower it takes to generate the code for that purpose. If you have a RegEx guru handy, it's almost always worthwhile as the patterns can easily be tweaked to accommodate for business rule changes without major loop refactoring which would likely be needed if you used pure java to do some of the complex things RegEx does.

If your basic line ending is the same everytime, such as with "magic", then you are better of using endsWith.
However, if you have a line that has the same base, but can have multiple values, such as:
<string> <number> <string> <string> <number>
where the strings and numbers can be anything, you're better of using RegEx.
Your lines are always ending with a string, but you don't know what that string is.

If it's as simple as endsWith, startsWith or contains, then you should use these functions. If you are processing more "complex" strings and you want to extract information from these strings, then regexp/matchers can be used.
If you have something like "commandToRetrieve someNumericArgs someStringArgs someOptionalArgs" then regexp will ease your task a lot :)

I'd never use regexes in java if I have an easier way to do it, like in this case the endsWith method. Regexes in java are as ugly as they get, probably with the only exception of the match method on String.
Usually avoiding regexes makes your core more readable and easier for other programmers. The opposite is true, complex regexes might confuse even the most experience hackers out there.
As for performance concerns: just profile. Specially in java.

If you are familiar with how regexp works you will soon find that a lot of problems are easily solved by using regexp.
Personally I look to using java String operations if that is easy, but if you start splitting strings and doing substring on those again, I'd start thinking in regular expressions.
And again, if you use regular expressions, why stop at lines. By configuring your regexp you can easily read entire files in one regular expression (Pattern.DOTALL as parameter to the Pattern.compile and your regexp don't end in the newlines). I'd combine this with Apache Commons IOUtils.toString() methods and you got something very powerful to do quick stuff with.
I would even bring out a regular expression to parse some xml if needed. (For instance in a unit test, where I want to check that some elements are present in the xml).
For instance, from some unit test of mine:
Pattern pattern = Pattern.compile(
"<Monitor caption=\"(.+?)\".*?category=\"(.+?)\".*?>"
+ ".*?<Summary.*?>.+?</Summary>"
+ ".*?<Configuration.*?>(.+?)</Configuration>"
+ ".*?<CfgData.*?>(.+?)</CfgData>", Pattern.DOTALL);
which will match all segments in this xml and pick out some segments that I want to do some sub matching on.

I would suggest using a regular expression when you know the format of an input but you are not necessarily sure on the value (or possible value(s)) of the formatted input.
What I'm saying, if you have an input all ending with, in your case, "magic" then String.endsWith() works fine (seeing you know that your possible input value will end with "magic").
If you have a format e.g a RFC 5322 message format, one cannot clearly say that all email address can end with a .com, hence you can create a regular expression that conforms to the RFC 5322 standard for verification.
In a nutshell, if you know a format structure of your input data but don't know exactly what values (or possible values) you can receive, use regular expressions for validation.

There's a saying that goes:
Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. (link).
For a simple test, I'd proceed exactly like you've done. If you find that it's getting more complicated, then I'd consider Regular Expressions only if there isn't another way.

Java Regex, capturing groups with comma separated values

InputString: A soldier may have bruises , wounds , marks , dislocations or other Injuries that hurt him .
ExpectedOutput:
bruises
wounds
marks
dislocations
Injuries
Generalized Pattern Tried:
".[\s]?(\w+?)"+ // bruises.
"(?:(\s)?,(\s)?(\w+?))*"+ // wounds marks dislocations
"[\s]?(?:or|and) other (\w+)."; // Injuries
The pattern should be able to match other input strings like: A soldier may have bruiser or other injuries that hurt him.
On trying the generalized pattern above, the output is:
bruises
dislocations
Injuries
There is something wrong with the capturing group for "(?:(\s)?,(\s)?(\w+?))*". The capturing group has one more occurences.. but it returns only "dislocations". "marks" and "dislocation: are devoured.
Could you please suggest what should be the right pattern, and where is the mistake?
This question comes closest to this question, but that solution didn't help.
Thanks.

When the capture group is annotated with a quantifier [ie: (foo)*] then you will only get the last match. If you wanted to get all of them then you need to quantifier inside the capture and then you will have to manually parse out the values. As big a fan as I am of regex, I don't think it's appropriate here for any number of reasons... even if you weren't ultimately doing NLP.
How to fix: (?:(\s)?,(\s)?(\w+?))*
Well, the quantifier basically covers the whole regex in that case and you might as well use Matcher.find() to step through each match. Also, I'm curious why you have capture groups for the whitespace. If all you are trying to do is find a comma-separated set of words then that's something like: \w+(?:\s*,\s*\w+)* Then don't bother with capture groups and just split the whole match.
And for anything more complicated re: NLP, GATE is a pretty powerful tool. The learning curve is steep at times but you have a whole industry of science-guys to draw from: http://gate.ac.uk/

Regex in not suited for (natural) language processing. With regex, you can only match well defined patterns. You should really, really abandon the idea of doing this with regex.
You may want to start a new question where you specify what programming language you're using to perform this task and ask for pointers there.
EDIT
PSpeed posted a promising link to a 3rd party library, Gate, that's able to do many language processing tasks. And it's written in Java. I have not used it myself, but looking at the people/institutions working on it, it seems pretty solid.

The pattern that works is: \w+(?:\s*,\s*\w+)* and then manually separate CSV
There is no other method to do this with Java Regex.
Ideally, Java regex is not suitable for NLP. A useful tool for text mining is: gate.ac.uk
Thanks to Bart K. , and PSpeed.