Choosing a Java Version on Ubuntu

When you have got multiple versions of Java installed, you can choose which one you want to use by running the update-alternatives command.

Running this command shows a list of installed Java JDKs and JREs allowing one to be selected as the default that is used when java needs to be executed.

$ sudo 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-7-openjdk-amd64/jre/bin/java   1051      manual mode
 
Press enter to keep the current choice[*], or type selection number: 2

To choose a default javac compiler, run the following command.

$ sudo update-alternatives --config javac

If you prefer to use a gui instead of the command line, you can execute galternatives instead and define the default versions of software with the following dialog.

$ sudo galternatives