usa questa guida che funziona benissimo
http://www.ubuntuforums.org/showthre...highlight=java

Download Java: http://java.sun.com/webapps/downloa...L?BundleId=9718

1. chmod a+x j2re-1_4_2_05-linux-i586.bin
2. ./j2re-1_4_2_05-linux-i586.bin
3. sudo mv j2re1.4.2_05 /usr/local/
4. sudo ln -sf /usr/local/j2re1.4.2_05/bin/java /usr/bin/java
5. sudo ln -sf /usr/local/j2re1.4.2_05/bin/java_vm /usr/bin/java_vm
6. cd /home/username/.mozilla/plugins

If you do not have a plugins directory you can create one.
mkdir -p /home/username/.mozilla/plugins

7. ln -s /usr/local/j2re1.4.2_05/plugin/i386/ns610-gcc32/libjavaplugin_oji.so libjavaplugin_oji.so
8. sudo ln -s /usr/local/j2re1.4.2_05/plugin/i386/ns610-gcc32/libjavaplugin_oji.so /usr/lib/mozilla-firefox/plugins/

That should give you working firefox java and systemwide java support.