Question

I am writing a program use JSP and Java. How can I use property files to support multiple languages?

And by the way, there are always some things like \u4345.
What is this? How do they come?

Answer 1

For the multiple languages, check out the ResourceBundle class.

About the \u4345, this is one of the dark and very annoying legacy corners of Java. The property files need to be in ASCII, so that all non-ASCII characters need to encoded as \uxxxx (their Unicode value). You can convert a file to use this encoding with the native2ascii command line tool.
If you are using an IDE or a build tool, there should be an option to invoke this automatically.

If the property file is something you have full control over yourself, you can starting from Java6 also use UTF-8 (or any other character set) directly in the property file, and specify that encoding when you load it:

// new in Java6
props.load(new InputStreamReader(new FileInputStream(file), 'UTF-8'));

Again, this only works if you load the Properties yourself, not if someone else does it, such as a ResourceBundle (used for internationalization).