Java doesn't work

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http://askubuntu.com – I was writing a program on my laptop to run on my server in Java. However, my laptop has java 7 running, my server java 6. This messed up. I tried to upgrade my server by installing openjdk-7-jre and openjdk-7-jdk packages. This didn't work. So I followed a guide helping me removing all java assosiated files and than re-install the needed packages. Something went wrong here.. I installed all the available java 7 packages and now I cannot use the java command anymore. I probably screwed up, does anyone knows how to fix it? I tested it with both the 7 and 6 install, nothing works anymore. Kind (HowTos)