[ubuntu] java not working

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http://ubuntuforums.org – dear all, I have now tried several times to download Java for either vpn connections or use of digital photoprinting software and other things, I have gone over the links from the official java homepage, the ubuntu wiki page and different online terminal codes, ... but it seems there still is no working java applet on my computer, i cannot activate java in my browser and don't know if there is any java installed after all or not. Q1: How do I delete old Java versions from my computer? Q2: How can I know what version of ubuntu my computer is currently running? Q3: What "type" of J (Hardware)