How to Install Java on Ubuntu: A Comprehensive Guide
Java is one of the most widely used programming languages around the world, especially in enterprise environments. It's required for many kinds of software, including the Android SDK, Apache Maven, and many server-side applications. In this blog post, we'll guide you through the process of installing Java on an Ubuntu system.
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:
sudo 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:
java -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:
sudo apt install default-jdk After the installation has finished, you can verify it by checking the Java version again:
java -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:
sudo apt install openjdk-8-jdk Again, verify the installation by checking the Java version:
java -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:
java -version To change the default version, use the update-alternatives command:
sudo 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:
sudo 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:
sudo nano /etc/environment At the end of this file, add the following line, replacing /path/to/java with the path you copied earlier:
JAVA_HOME="/path/to/java" Save and close the file. Load the environment variable into the current session with the following command:
source /etc/environment You can now check that JAVA_HOME has been set correctly by running:
echo $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!