You can certainly view Japanese and Chinese characters produced by Java (say on in a web application) on an English Windows installation and input those characters with installation of the appropriate Langues and Input methods. You configure those on Windows from the "Regional and Language Options" on the control panel.
Inputting those characters from a web application generally requires the use of an appropriate character set (like UTF-8) for conversion from bytes to Java strings.
Storing in a database would require an appropriate database character set.
You might want to check out the links here:
http://www.i18ngurus.com/docs/984813264.html, especially the first one which provides a link to Sun's i18n tutorial.
You might want to give more details of what kind of application you're writing (Swing, Web app, database storage?) for people to provide more hints.
Tim