apt-cache policy command:
$ apt-cache policy openjdk-6-jre
500 http://aptmirror.fqdn/ubuntu/ trusty-security/universe amd64 Packages
500 http://aptmirror.fqdn/ubuntu/ trusty/universe amd64 Packages
It says that I don't have any version installed, and of the available versions,
6b32-1.13.4-4ubuntu0.14.04.1 (the candidate) will be installed if I do
sudo apt-get install openjdk-6-jre.
Even if you have it installed already, if you do
sudo apt-get install openjdk-6-jre, the latest version available (according to the Candidate field above) will be installed. So an installed package will be upgraded.
You can press CtrlC to exit from most programs, including
sudo password prompts and
apt-get. It's a very bad idea to do so with
apt-get. You can cancel while the download is in progress, but once the installation begins, don't do so.