How do I change Java Version without "sudo"?

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http://askubuntu.com – Sorry for my bad English, but I'm really trying to be better. Ok. I've created a new command/alias(changejava) on Ubuntu 12.04, and I need to skip "sudo password" only when I write "$changejava". If I write "$changejava" using terminal, Ubuntu show me what can I do. I just need to press 0, 1 or 2. But if I press anything, terminal says: "update-alternatives: to use /usr/lib/jvm/java-6-sun/jre/bin/java to provide /usr/bin/java (java). update-alternatives: error: Could not create file '/var/lib/dpkg/alternatives/java.dpkg-tmp': Denied. " If I try "$sudo changejava", I have: "Type jessegasp (HowTos)