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-amd64You’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 modeCheck 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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