Since Sun’s API search is a real pain in the arse and even DocWeb doesn’t allow you to quickly search the Java API, this firefox plugin is a substantial improvement: https://addons.mozilla.org/en-US/firefox/addon/60675/
It basically redirects the search query to Google’s “I’m Feeling Lucky” feature to search Java’s API for the class information.
Together with Second Search querying the Java API is now lightning fast: https://addons.mozilla.org/en-US/firefox/addon/4096/
Since Mozilla dropped support on OJI (Open Java Virtual Machine Integration), the classic java plugin file javaplugin-oji.so doen’t work anymore for Firefox versions >3.6. Starting in Firefox 3.6, Mozilla will only support the standard NPAPI and NPRuntime interfaces.
However, a ‘Next-Generation Java plugin’ (that’s what Sun calls it) is available in Java version 6 update 10 or newer and supports the NPAPI and NPRuntime interfaces.
Installation is quite simple. Remove the symbolic links to libjavaplugin_oji.so from the Firefox plugins directory and replace it with to libnpjp2.so:
rm -f libjavaplugin_oji.so
ln -s <JRE>/lib/i386/libnpjp2.so .
where <JRE> is the path to your Java runtime environment.