Yes, I have Java installed :

$>java -showversion
java version "1.4.2-02"
Java(TM) 2 Runtime Environment, Standard Edition (build Blackdown-1.4.2-02)
Java HotSpot(TM) 64-Bit Server VM (build Blackdown-1.4.2-02, mixed mode)

But I'm not sure I have firefox plugin :

$ >/usr/lib/mozilla-firefox/components# ls
accessibility-atk.xpt   libcookie.so            necko.xpt
accessibility.xpt       libdocshell.so          nsCloseAllWindows.js
appshell.xpt            libeditor.so            nsDictionary.js
autocomplete.xpt        libembedcomponents.so   nsExtensionManager.js
autoconfig.xpt          libfileview.so          nsFilePicker.js
bookmarks.xpt           libgfx_gtk.so           nsHelperAppDlg.js
caps.xpt                libgfxps.so             nsInterfaceInfoToIDL.js
chardet.xpt             libgklayout.so          nsProgressDialog.js
commandhandler.xpt      libgkplugin.so          nsProxyAutoConfig.js
composer.xpt            libhtmlpars.so          nsResetPref.js
compreg.dat             libi18n.so              nsSidebar.js
content_base.xpt        libimglib2.so           nsUpdateService.js
content_htmldoc.xpt     libjar50.so             nsXmlRpcClient.js
content_html.xpt        libjsd.so               oji.xpt
content_xmldoc.xpt      libmork.so              passwordmgr.xpt
content_xslt.xpt        libmozfind.so           pipboot.xpt
cookie.xpt              libnecko2.so            pipnss.xpt
directory.xpt           libnecko.so             pippki.xpt
docshell.xpt            libnegotiateauth.so     plugin.xpt
dom_base.xpt            libnsappshell.so        prefetch.xpt
dom_core.xpt            liboji.so               pref.xpt
dom_css.xpt             libpipboot.so           profile.xpt
dom_events.xpt          libpipnss.so            progressDlg.xpt
dom_html.xpt            libpippki.so            proxyObjInst.xpt
dom_loadsave.xpt        libpref.so              rdf.xpt
dom_range.xpt           librdf.so               satchel.xpt
dom_stylesheets.xpt     libsystem-pref.so       search.xpt
dom_traversal.xpt       libtoolkitcomps.so      shellservice.xpt
dom_views.xpt           libtransformiix.so      shistory.xpt
dom_xbl.xpt             libtxmgr.so             sidebar.xpt
dom_xpath.xpt           libtypeaheadfindsea.so  toolkitprofile.xpt
dom.xpt                 libuconv.so             txmgr.xpt
dom_xul.xpt             libucvmath.so           txtsvc.xpt
downloads.xpt           libuniversalchardet.so  typeaheadfindsea.xpt
editor.xpt              libwebbrwsr.so          uconv.xpt
embed_base.xpt          libwebsrvcs.so          unicharutil.xpt
extensions.xpt          libwidget_gtk2.so       update.xpt
exthandler.xpt          libxmlextras.so         uriloader.xpt
fastfind.xpt            libxpcom_compat_c.so    webBrowser_core.xpt
filepicker.xpt          libxpconnect.so         webbrowserpersist.xpt
find.xpt                libxpinstall.so         webshell_idls.xpt
gfx.xpt                 libxremote_client.so    websrvcs.xpt
helperAppDlg.xpt        libxremoteservice.so    widget.xpt
history.xpt             locale.xpt              windowds.xpt
htmlparser.xpt          lwbrk.xpt               windowwatcher.xpt
imglib2.xpt             migration.xpt           xmlextras.xpt
intl.xpt                mimetype.xpt            xml-rpc.xpt
jar.xpt                 mozbrwsr.xpt            xpcom_base.xpt
jsconsole-clhandler.js  mozfind.xpt             xpcom_components.xpt
jsconsole.xpt           necko_about.xpt         xpcom_ds.xpt
jsdservice.xpt          necko_cache.xpt         xpcom_io.xpt
jsurl.xpt               necko_cookie.xpt        xpcom_obsolete.xpt
layout_base.xpt         necko_data.xpt          xpcom_threads.xpt
layout_xul_tree.xpt     necko_dns.xpt           xpcom_xpti.xpt
layout_xul.xpt          necko_file.xpt          xpconnect.xpt
libaccessibility.so     necko_ftp.xpt           xpinstall.xpt
libappcomps.so          necko_http.xpt          xpti.dat
libautoconfig.so        necko_jar.xpt           xremoteservice.xpt
libbrowsercomps.so      necko_res.xpt           xuldoc.xpt
libcaps.so              necko_socket.xpt        xultmpl.xpt
libchrome.so            necko_strconv.xpt
libcomposer.so          necko_viewsource.xpt