Ubuntu 26.04 ships with OpenJDK 25 as its default Java version. However, many applications and frameworks require a specific older version such as OpenJDK 8, 11, 17, or 21. In this guide, you will learn how to install a specific Java version on Ubuntu 26.04, manage multiple Java installations side by side, and switch between them using the update-alternatives system. Whether you need to java install Ubuntu 26.04 with a particular version for legacy software or development compatibility, this tutorial covers the complete process.

Software Requirements

Check Available Java Versions on Ubuntu 26.04

Before installing a specific Java version, it is useful to check which OpenJDK packages are available in the Ubuntu 26.04 repositories. This ensures you are installing a version that is officially supported and maintained.

1. List available OpenJDK packages: Use apt search to find all available OpenJDK packages in the repositories.

   $ apt search openjdk | grep '^openjdk-[0-9]*-jdk/'

   On Ubuntu 26.04, you will see packages for OpenJDK 8, 11, 17, 21, and 25.

2. Check currently installed Java: If you have already installed Java on Ubuntu 26.04 using the default packages, verify which version is currently active.

   $ java -version

Install a Specific Java Version on Ubuntu 26.04

To java install Ubuntu 26.04 with a particular OpenJDK version, use the version-specific package name. The naming convention follows the pattern openjdk-{version}-jdk for the full development kit or openjdk-{version}-jre for the runtime only.

1. Update the package index:

   $ sudo apt update

2. Install the desired version: Replace the version number with the one you need. For example, to install OpenJDK 17:

   $ sudo apt install openjdk-17-jdk

   Similarly, for other versions:

   $ sudo apt install openjdk-8-jdk
   $ sudo apt install openjdk-11-jdk
   $ sudo apt install openjdk-21-jdk

3. Verify the installation: After the installation completes, confirm that the new version is available on your system.

   $ /usr/lib/jvm/java-17-openjdk-amd64/bin/java -version

   This calls the specific binary directly rather than the system default.

   👁 Terminal showing /usr/lib/jvm/ directory listing with OpenJDK 8 and 17 installed and direct version check confirming OpenJDK 17.0.18
   

Switch Between Java Versions on Ubuntu 26.04

When multiple Java versions are installed, Ubuntu uses the update-alternatives system to manage which one is active. This system controls the /usr/bin/java and /usr/bin/javac symlinks, so you do not need to modify your PATH. Consequently, switching versions is simply a matter of running a single command.

1. Select the default Java runtime: Run the following command and choose the version you want to use.

   $ sudo update-alternatives --config java

   You will see a numbered list of all installed Java versions. Enter the selection number corresponding to the version you want to activate.

2. Select the default Java compiler: If you installed the JDK, you should also switch the compiler to match.

   $ sudo update-alternatives --config javac

3. Verify the switch: Confirm that the system now uses the selected version.

   $ java -version
   $ javac -version

Update JAVA_HOME for the Active Version

While update-alternatives handles the /usr/bin/java and /usr/bin/javac symlinks automatically, the JAVA_HOME environment variable is not updated by the system. Many build tools and frameworks such as Maven, Gradle, and Apache Spark rely on this variable to locate the Java installation. Therefore, you need to ensure it points to the correct version after switching.

The recommended approach is to set JAVA_HOME dynamically so it always follows the active version selected by update-alternatives:

1. Set dynamic JAVA_HOME: Add the following line to your ~/.bashrc file. This resolves the active java binary path and derives the JDK root directory automatically.

   $ echo 'export JAVA_HOME=$(dirname $(dirname $(readlink -f $(which java))))' >> ~/.bashrc
   $ source ~/.bashrc

   With this in place, every time you switch versions using update-alternatives, JAVA_HOME will reflect the change after opening a new terminal session.

2. Verify JAVA_HOME:

   $ echo $JAVA_HOME

Alternatively, if you prefer to set JAVA_HOME to a specific path manually, you can use sed to update it in your ~/.bashrc each time you switch:

$ sed -i 's|export JAVA_HOME=.*|export JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64|' ~/.bashrc
$ source ~/.bashrc

Remove a Java Version from Ubuntu 26.04

If you no longer need a particular Java version, you can remove it to free up disk space. The update-alternatives system will automatically adjust the default to the next available version.

1. Remove the unwanted version: For example, to remove OpenJDK 8:

   $ sudo apt remove openjdk-8-jdk openjdk-8-jre

2. Clean up unused dependencies:

   $ sudo apt autoremove

3. Confirm the remaining versions: Verify which Java versions are still installed.

   $ update-alternatives --list java

Conclusion

You now know how to install a specific Java version on Ubuntu 26.04, manage multiple versions simultaneously, and switch between them using update-alternatives. This flexibility is essential when working with applications that require different Java versions, from legacy software needing OpenJDK 8 to modern frameworks requiring OpenJDK 21 or 25.

For the basic installation of the default Java version, see our guide on how to install Java on Ubuntu 26.04. For additional details on available OpenJDK packages, consult the official Ubuntu Java documentation.

Frequently Asked Questions

1. Can I have multiple Java versions installed at the same time on Ubuntu 26.04? Yes. Ubuntu supports installing multiple OpenJDK versions side by side. Each version is installed in its own directory under /usr/lib/jvm/. You use update-alternatives to control which version is the system default.
2. How do I check all Java versions installed on my system? Run update-alternatives --list java to see all registered Java installations. This will list the full path to each installed version.
3. What is the difference between auto and manual mode in update-alternatives? In auto mode, the system automatically selects the highest-priority version. In manual mode, the system uses whichever version you explicitly selected. Running sudo update-alternatives --config java and choosing a version sets it to manual mode.
4. Do I need to switch javac separately from java? Yes. The java runtime and javac compiler are managed as separate alternatives. After switching java, you should also run sudo update-alternatives --config javac to match the compiler version.
5. Will removing a Java version break other installed versions? No. Each OpenJDK version is packaged independently. Removing one version does not affect others. The update-alternatives system will automatically select the next available version as the default.