Isso funcionou para mim
# update-alternatives --config javaws
There are 2 choices for the alternative javaws (providing /usr/bin/javaws).
Selection Path Priority Status
------------------------------------------------------------
0 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javaws 1061 auto mode
1 /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/javaws 1061 manual mode
* 2 /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/javaws 1060 manual mode
Press enter to keep the current choice[*], or type selection number: 2
Infelizmente não é o meu cérebro, mas copiado daqui link