Sometime is needed to install different JVM on Ubuntu server due to application compatibility or software development purposes. To switch between different JVM in ubuntu from command line, use this command:

sudo update-alternatives --config java

and this menu will appear:

There are 2 choices for the alternative java (providing /usr/bin/java).
 
  Selection    Path                                            Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      auto mode
  1            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-7-openjdk-amd64/jre/bin/java   1071      manual mode