Ubuntu 20.04 / Debian - switch default java version

In this short article, we would like to show how to switch the default Java version into a different one under Ubuntu 20.04 / Debian linux.

Quick solution (run the following command to open configuration):

sudo update-alternatives --config java

Note: command will list and ask us to select an active Java version.

Practical example

The example shows switching from Java 14 to Java 8.

$ java -version
openjdk version "14.0.2" 2020-07-14
OpenJDK Runtime Environment (build 14.0.2+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 14.0.2+12-Ubuntu-120.04, mixed mode, sharing)

john@john-pc:~$ 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-14-openjdk-amd64/bin/java      1411      auto mode
* 1            /usr/lib/jvm/java-14-openjdk-amd64/bin/java      1411      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java   1081      manual mode

Press <enter> to keep the current choice[*], or type selection number: 2

update-alternatives: using /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java to provide /usr/bin/java (java) in manual mode

john@john-pc:~$ java -version
openjdk version "1.8.0_275"
OpenJDK Runtime Environment (build 1.8.0_275-8u275-b01-0ubuntu1~20.04-b01)
OpenJDK 64-Bit Server VM (build 25.275-b01, mixed mode)

john@john-pc:~$