On my current project, we are using properties files for strings. Those strings are then "formatted" using MessageFormat. Unfortunately, MessagFormat has a handling of single quotes that becomes a bit of a hindrance in languages, such as French, which use a lot of apostrophes.
For instance, suppose we have this entry
login.userUnknown=User {0} does not exist
When this gets translated into French, we get:
login.userUnknown=L'utilisateur {0} n'existe pas
This, MessageFormat does not like...
And I, do not like the following, i.e. having to use double quotes:
login.userUnknown=L''utilisateur {0} n''existe pas
The reason I don't like it is that it causes spellchecking errors everywhere.
Question: I am looking for an alternative to the instruction below, an alternative that does not need doubling quotes but still uses positional placeholders ({0}, {1}…). Is there anything else that can I use?
MessageFormat.format(Messages.getString("login.userUnkown"), username);
No there is no other way as it is how we are supposed to do it according to the javadoc.
A single quote itself must be represented by doubled single quotes '' throughout a String
As workaround, what you could do is doing it programmatically using replace("'", "''") or for this particular use case you could use the apostrophe character instead which is ’ it would be even more correct actually than using a single quote.
Probably too late for you, but someone else might find this useful: Instead of Java's MessageFormat, use ICU (International Components for Unicode) (or rather its Java port ICU4J). It's basically a set of tools and data to support you in internationalizing your application. And among those tools is their own version of MessageFormat. It's very similar (maybe even backwards compatible) and can handle single quotes exactly like you want it. It can even handle doubled/escaped single quotes so you can try it as a drop-in replacement for Java's MessageFormat without having to unescape your single quotes first.
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)
Is there a tool to convert a regex from one popular language's syntax to another? For example a Python-style regex to a Java-style regex?.
Or at least, has someone put together a set of rules to do these conversions?
And obviously some constructs won't be able to convert.
Go to this article, and follow the link to "Regex info's comparison of Regex flavors", that got me to a tool called RegexBuddy, which sounds like it might do what you want.
Yes there is a Windows tool that will do this: RegexBuddy
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.
This question is pretty much the same as this .Net question exept for java.
How do you escape the %1$ characters in a java String.format?
THe reason I need to do this is that I'm building up a string that will later have more info inserted into it. I've thought of having one of the args just be "%1$" but that doesn't seem to be very elegant?
sorry if this is obvious my java is a tad rusty.
You can just double up the %
Either you can use the proposal of Draemon, either you can also have a look at java.text.MessageFormat class that has more powerfull formatting abilities than String.format()