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How to Install Java on Ubuntu (2026 Guide) – Complete DevOps Engineer Tutorial

Introduction

Java remains one of the most widely used programming languages in the world. From enterprise applications and banking systems to modern microservices, big data platforms, and cloud-native applications, Java powers thousands of production environments every day.

If you are a developer, system administrator, DevOps engineer, or cloud engineer, knowing how to properly install and manage Java on Linux is an essential skill.

Many beginners simply run a package installation command and move on. However, production environments often require specific Java versions because applications may not be compatible with newer releases.

In this complete guide, you'll learn how to install Java on Ubuntu, verify the installation, configure environment variables, manage multiple Java versions, and follow real DevOps best practices used in enterprise environments.

Real DevOps Story: Application Failed After Java Upgrade

During a production migration project, one team upgraded Java from version 11 to version 21 because they wanted the latest performance improvements.

The upgrade seemed successful at first.

However, after deployment, the application started throwing compatibility errors. A third-party library used by the application was certified only for Java 11 and failed to load correctly.

The production environment became unstable, resulting in downtime and emergency rollback procedures.

Lesson Learned: Never upgrade Java in production without testing application compatibility. Always verify supported Java versions before deployment.

This is why experienced DevOps engineers maintain strict version control and test upgrades in staging environments first.

What is Java and Why Is It Important?

Java is a high-level, object-oriented programming language designed to run on multiple platforms using the Java Virtual Machine (JVM).

Today, Java is used in:

  • Enterprise applications
  • Spring Boot microservices
  • Banking systems
  • Big data platforms
  • Android development
  • Cloud-native applications
  • DevOps automation tools

Many popular platforms such as Jenkins, Hadoop, Kafka, Elasticsearch, and numerous enterprise systems require Java.

Step 1: Update Ubuntu Packages

Before installing Java, update your package repositories.

sudo apt update && sudo apt upgrade -y

This ensures Ubuntu installs the latest available packages and security updates.

Step 2: Check Existing Java Installation

Before installing Java, verify whether Java is already available on your system.

java -version

If Java is not installed, you may see an error similar to:

Command 'java' not found

This confirms that Java needs to be installed.

Step 3: Install Java on Ubuntu

The easiest and most reliable method is installing OpenJDK from Ubuntu repositories.

Install Latest OpenJDK

sudo apt install default-jdk -y

This installs the default Java Development Kit maintained by Ubuntu.

Install Java 21

sudo apt install openjdk-21-jdk -y

Java 21 is currently a popular Long-Term Support (LTS) release for enterprise environments.

Install Java 17

sudo apt install openjdk-17-jdk -y

Many organizations still standardize on Java 17 because of long-term support and application compatibility.

Install Java Runtime Only

If you only need to run Java applications and not compile code:

sudo apt install default-jre -y

Step 4: Verify Java Installation

After installation, verify Java is working correctly.

java -version

Example output:


openjdk version "21.0.7"
OpenJDK Runtime Environment
OpenJDK 64-Bit Server VM

Verify the compiler as well:

javac -version

Example:

javac 21.0.7

Step 5: Configure JAVA_HOME Environment Variable

Many enterprise applications require the JAVA_HOME environment variable.

Find the Java installation path:

sudo update-alternatives --config java

Example output:

/usr/lib/jvm/java-21-openjdk-amd64/bin/java

Open the profile file:

nano ~/.bashrc

Add the following lines:


export JAVA_HOME=/usr/lib/jvm/java-21-openjdk-amd64
export PATH=$PATH:$JAVA_HOME/bin

Reload the configuration:

source ~/.bashrc

Verify:

echo $JAVA_HOME

Step 6: Manage Multiple Java Versions

Many DevOps environments require multiple Java versions.

Check installed Java versions:

update-java-alternatives --list

Switch Java versions:

sudo update-alternatives --config java

You will see a numbered list of installed Java versions.

Select the desired version and press Enter.

Verify the active version:

java -version

This capability is extremely useful when maintaining legacy and modern applications on the same server.

Important Java Commands

Command Purpose Description
java -version Check version Displays installed Java version
javac -version Compiler version Shows Java compiler version
which java Locate Java Shows Java binary location
echo $JAVA_HOME Check variable Displays JAVA_HOME path
update-alternatives --config java Switch version Select active Java version
jar -tf app.jar View archive Lists contents of JAR file

DevOps Best Practices

  • Use LTS Java releases for production systems
  • Always test Java upgrades in staging environments
  • Document Java versions in deployment documentation
  • Configure JAVA_HOME consistently across servers
  • Use Infrastructure as Code for Java installation
  • Monitor application logs after Java upgrades
  • Keep security patches up to date
  • Avoid upgrading production servers directly

In most enterprise environments, Java version management is part of the CI/CD deployment process to ensure consistency across development, staging, and production environments.

Common Errors and Fixes

Error Cause Solution
java: command not found Java not installed Install OpenJDK package
JAVA_HOME not set Missing environment variable Configure JAVA_HOME
Wrong Java version Multiple versions installed Use update-alternatives
Application startup failed Unsupported Java version Verify application compatibility
Permission denied Insufficient privileges Use sudo where required

Frequently Asked Questions

1. Which Java version should I use for production?

Java LTS releases such as Java 17 or Java 21 are recommended because they receive long-term security and maintenance updates.

2. What is the difference between JDK and JRE?

JDK includes development tools such as the Java compiler, while JRE is only required to run Java applications.

3. Can I install multiple Java versions?

Yes. Ubuntu allows multiple Java versions to coexist, and you can switch between them using update-alternatives.

4. Is OpenJDK free?

Yes. OpenJDK is open-source and widely used in enterprise environments.

5. Why is JAVA_HOME important?

Many Java applications, build tools, and CI/CD pipelines depend on JAVA_HOME to locate the Java installation.

6. How do I uninstall Java?

sudo apt remove openjdk-* -y

This removes installed OpenJDK packages from the system.

Conclusion

You now know how to install Java on Ubuntu, configure JAVA_HOME, manage multiple Java versions, and apply production-ready DevOps practices.

Whether you're deploying Spring Boot applications, managing Jenkins servers, building CI/CD pipelines, or running enterprise workloads, proper Java management is a critical skill.

By following the steps in this guide, you can maintain stable, secure, and predictable Java environments across development, staging, and production systems.

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