How to switch between installed Java VM in Ubunutu

Java Mascot

Imagine you have installed both IcedTea and Oracle (Sun) JVM and you want to switch to Sun JVM from IcedTea. This can be done with command 'update-alternatives --config java' as root.

root@kassendra:/opt# java -version
java version "1.6.0_20"
OpenJDK Runtime Environment (IcedTea6 1.9.7) (6b20-1.9.7-0ubuntu1~10.04.1)
OpenJDK Server VM (build 19.0-b09, mixed mode)
root@Kassendra:/opt# update-alternatives --config java 
There are 2 choices for the alternative java (providing /usr/bin/java).

  Selection    Path                                      Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-6-openjdk/jre/bin/java   1061      auto mode
  1            /usr/lib/jvm/java-6-openjdk/jre/bin/java   1061      manual mode
  2            /usr/lib/jvm/java-6-sun/jre/bin/java       63        manual mode

Press enter to keep the current choice[*], or type selection number: 2
update-alternatives: using /usr/lib/jvm/java-6-sun/jre/bin/java to provide /usr/bin/java (java) in manual mode.
root@kassendra:/opt# java -version
java version "1.6.0_24"
Java(TM) SE Runtime Environment (build 1.6.0_24-b07)
Java HotSpot(TM) Server VM (build 19.1-b02, mixed mode)
root@kassendra:/opt#