internationalization

Is it necessary to install the appropriate font to display the unicode characters..
plz reply..

Sometimes. It depends which characters you want to use. Here is a table showing which alphabets are already supported by default using Sun's JRE. Note that this does not apply to System.out, where you often have a much smaller subset of displayable characters - but that's really dependant on how your system is configured. If you want to display anything you don't normally see printed on your console, you're probably best off displaying it using one of the swing/awt components for displaying text, like JTextArea. That will make use of whatever fonts have been installed. Read more about fonts in the documentation.