Hmmm... I guess it depends on your situation and what you're trying to do. It sounds to me like you shouldn't need to convert to any other character set at all - the Unicode
string already represents Kanji "characters". The only problem is, if you want your browser to be able to display the Kanji, you must make sure that the you have the necessary fonts installed. Your best bet is to consult the documentation
here. (Note that the links Sean and I give are for JDK 1.1 - if you know that your users will have a plugin for 1.2, you can find other appropriate docs in the release notes at
www.javasoft.com/docs . Alternately, you might try bypassing the JDK and installing the proper font support in the OS - if you're using Windows and Internet Explorer, go to
windowsupdate.microsoft.com and download the Japanese Language support update.
Another thing to try - if you're building a GUI which is to display these characters, try using the
setLocale() method of Component to set the locale to Locale.JAPAN. This should enable the component to find the right fonts to display Japanese characters.
As for other encodings such as those provided in the i18n.jar file,
you should only need those if you're working with other applications which are unable to use Unicode. For example if you need to read/write files which are encoded in ShiftJIS rather than Unicode, you'll need the jar file. Aside from the String constructors Sean mentioned, the standard way to specify an encoding is through an InputStreamReader or OutputStreamWriter constructor.
Good luck!