Switching between installed Java versions can be accomplished using the update alternatives command.

• To get a list of your installed Java platforms, run the following command from the terminal:

  sudo update-alternatives --config java

  This will give you a list output similar to this:

  There are 2 choices for the alternative java (providing /usr/bin/java).SelectionPathPriorityStatus------------------------------------------------------------0/usr/lib/jvm/java-6-oracle/jre/bin/java         1070auto mode  1/usr/lib/jvm/java-7-openjdk-i386/jre/bin/java   1051      manual mode*2/usr/lib/jvm/java-6-openjdk-i386/jre/bin/java   1069      manual modePress enter to keep the current choice[*], or type selection number:

In this case, the Open JDK 6 version is running. To switch to the Open JDK version 7, you would select option 1 at the prompt and press the Enter key.

You will now be running the OpenJDK 7 version. No other changes will be needed to switch your Java versions.