How to Install Java on Ubuntu: A Comprehensive Guide

Prerequisites

Before we start, make sure you have a system running Ubuntu. You should also have administrative access to this system so you can install packages.

Step 1: Update Your System

Before you install any package on your Ubuntu system, it's good practice to update the system packages. You can do this by running the following commands:

codesudo apt update sudo apt upgrade 

Step 2: Check for Existing Java Installation

Before installing Java, it's worth checking to see if it's already installed on your system. You can do this by running:

codejava -version 

If Java is installed, you'll see the installed version. If it isn't, you'll get a message indicating that Java is not currently installed.

Step 3: Installing the Default JDK

The easiest way of installing Java on Ubuntu is to use the default JDK (Java Development Kit) in the Ubuntu repository. As of writing, this is OpenJDK 11. You can install this by running:

codesudo apt install default-jdk 

After the installation has finished, you can verify it by checking the Java version again:

codejava -version 

You should now see that OpenJDK 11 has been installed.

Step 4: Installing a Different Java Version

If you need a different version of Java, you can use the Ubuntu package manager to install it. For example, to install OpenJDK 8, you could run:

codesudo apt install openjdk-8-jdk 

Again, verify the installation by checking the Java version:

codejava -version 

Step 5: Setting the Default Java Version

If you have more than one version of Java installed, you can select the default version using the update-alternatives command. You can check the current default version by running:

codejava -version 

To change the default version, use the update-alternatives command:

codesudo update-alternatives --config java 

You'll see a list of all installed Java versions. Just enter the number of the version you want to use as the default and hit Enter.

Step 6: Setting JAVA_HOME Environment Variable

Many Java-based applications use the JAVA_HOME environment variable to determine which Java installation to use. After installing Java, it's a good idea to set this variable.

First, find out where Java is installed:

codesudo update-alternatives --config java 

This will display a list of installed Java versions and their paths. Copy the path for your preferred installation, but exclude the bin/java part at the end.

Next, open /etc/environment in a text editor with root privileges:

codesudo nano /etc/environment 

At the end of this file, add the following line, replacing /path/to/java with the path you copied earlier:

codeJAVA_HOME="/path/to/java" 

Save and close the file. Load the environment variable into the current session with the following command:

codesource /etc/environment 

You can now check that JAVA_HOME has been set correctly by running:

codeecho $JAVA_HOME 

This should display the path to your Java installation.

Conclusion

Java is a versatile and powerful programming language that's used in many different kinds of software. Whether you're planning to do Java development or just need to run some Java software, installing Java on your Ubuntu system is straightforward.

By following the steps above, you should now have Java installed and ready to use. You've also learned how to set the default Java version and set the JAVA_HOME environment variable, which is important for many Java-based applications.

This guide should have given you a strong foundation for working with Java on Ubuntu. Whether you're developing software, setting up a server, or just tinkering with your system, knowing how to manage your Java installation is an important skill.

Happy coding! Remember, the Java world is vast and there's always more to learn, so don't stop exploring!