How to set default Java version on Ubuntu / Debian

In this guide, I’ll show you how you can set the default Java version on Ubuntu / Debian Linux system. It is common to run more than one version of Java in your Ubuntu or Debian system – For development reasons or varying applications requirements.

Earlier on we had done an article on installing Java on Ubuntu / Debian:

• How to Install Java 11 on Ubuntu
• How to Install Java 8 on Ubuntu
• Install Java 17 (OpenJDK 17) on Debian

Suppose you install Java 11 and you had another version of Java installed earlier, you can select default Java version to use using the update-alternatives --config java command.

Step 1: Checking Java versions installed on Ubuntu / Debian

To get a list of installed Java versions, run the command:

$ sudo update-java-alternatives --list
java-1.11.0-openjdk-amd64      1111       /usr/lib/jvm/java-1.11.0-openjdk-amd64
java-1.8.0-openjdk-amd64       1081       /usr/lib/jvm/java-1.8.0-openjdk-amd64

You’ll get a list of all Java editions that are installed on your Debian / Ubuntu system. Identify the version you wan to change to then proceed to next step.

Step 2: Set default Java version on Ubuntu / Debian

Once you have a list of Java version, set a default one by running the command. I’ll change mine from Java 11 to Java 8:

$ 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-11-openjdk-amd64/bin/java      1111      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/java      1111      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

Check Java version

$ java -version
openjdk version "1.8.0_302"
OpenJDK Runtime Environment (build 1.8.0_302-8u302-b08-0ubuntu2-b08)
OpenJDK 64-Bit Server VM (build 25.302-b08, mixed mode)

The same can be done for javac.

$ sudo  update-alternatives --config javac
There are 2 choices for the alternative javac (providing /usr/bin/javac).

  Selection    Path                                          Priority   Status
------------------------------------------------------------
* 0            /usr/lib/jvm/java-11-openjdk-amd64/bin/javac   1111      auto mode
  1            /usr/lib/jvm/java-11-openjdk-amd64/bin/javac   1111      manual mode
  2            /usr/lib/jvm/java-8-openjdk-amd64/bin/javac    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/bin/javac to provide /usr/bin/javac (javac) in manual mode

If JAVA_HOME is not set correctly, run the command below to set from current default Java configured:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

For JRE, use:

export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:jre/bin/java::")

Persistence can be achieved by placing the export command in your .bashrc or /etc/profilefile.

$ vim ~/.bashrc
export JAVA_HOME=$(readlink -f /usr/bin/java | sed "s:bin/java::")

We hope this article helped you to set the default Java version on Ubuntu / Debian Linux system. Stay connected for more articles on Java and Development tools.

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