Inserting numbers in strings

Question

Back in the good old days of C programming we could use printf to insert a number into a printed string at run time. Just stick "%i" or "%f" in the string where you want the number to appear.
Is there any way to do something similar with Java internationalization? Let's say I want to print out an error message with an integer stuck somewhere in the middle. The position where that integer needs to be inserted can very based on the language. I can create two different Java string resources, one before the number and one after, and then string them together in code. But that seems a little awkward. Is there a better way?
I heard a rumor that "printf" type functionality might be coming in a future JDK release so maybe we just have to wait.

Answer 1

First of all, you SHOULD NOT create two string resources and stick them together - that makes the localisation process very difficult since the localisers can take the two strings separately and not realise they're meant to be together; and what happens if you have 3 variables you want to put in a string? That gets far more complicated.
The class you want to use is java.text.MessageFormat. That takes a 'pattern' and an array of objects and inserts the objects into the pattern in the places that pattern specifies.
Here's an example. Say you want a message to say 'There are X files in the folder called Y' (obviously this needs to be localised). You would store the following pattern as one piece of text in a resource bundle:There are {0} files in the folder called {1}Note the curly braces containing numbers - these are the places where the variables will be inserted.
To use the message, you retrieve it from the resource bundle (I assume you know how to do this) and ask MessageFormat to insert the variables, like this:String pattern = <get the pattern from the ResourceBundle>;
Integer numFiles = new Integer(1234);
String folderName = "MyFolder";
Object[] variables = new Object[] { numFiles, folderName };
String message = MessageFormat.format(pattern, variables);This will format the given pattern using the default Locale.
It may seem vastly more complicated than C's printf, but it's also more flexible and powerful - take a look at the API docs for MessageFormat for more information.
Hope this helps.
Alistair