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How to install Java (JDK and JRE) on Ubuntu 20.04 LTS

Java is the most widely used programming language. It can be used to create server and desktop applications and Java runs on almost all operating systems like Mac OS, Windows, and Linux. Java applications are also used on game consoles and on Mobile phones, e.g. the Android operating system uses Java as an app programming language. Java is open-source and has two variants, the JDK (Java development kit) which is required when you plan to develop Java applications and the JRE (Java Runtime Environment) which is used to run java applications, so it does not contain compilers and development tools.

This article shows the installation of Java 8 and Java 11 JDK and JRE on Ubuntu 20.04 using the terminal and how to switch between these two versions. All the command and steps are executed in this article on Ubuntu 20.04 Linux system which is mentioned below.

Installation of Java on Ubuntu 20.04

Open the terminal on your system using ‘Ctrl + Alt+ t’ or through the application search bar as follows:

Linux Terminal

To start the installation of Java on Ubuntu 20.04 first, you need to update the apt repository on your system using the following command:

$ sudo apt update

Now, check that Java is installed on your system or not using the following command:

$ Java --version

If Java is already installed on your system, then the following output will be displayed on your terminal window:

Check Java Version

By default, Ubuntu 20.04 includes the Java 11 JDK. If Java is not installed on your system then use the following command to install the Java JDK.

$ sudo apt install default-jdk

or

$ sudo apt install openjdk-11-jdk

Install Java JDK

The above command will install the default version of Java JDK-11 on your system.

Now, you can check the installed version using the following command:Advertisements

$ Java --version

Some older java applications might require the previous Java version If your application requires the JDK-8 version then you can install it using the following command:

$ sudo apt install openjdk-8-jdk

Install Java 8 on Ubuntu 20.04

After executing the above command, the Java JDK-8 installation will begin on your system and it will take some time to complete the installation process. So, after that you can Java version using the following command:

$ Java --version

Set Default Java version on Ubuntu 20.04

If multiple Java versions installed on your system Ubuntu 20.04, then you can check the default Java version using the command as follows:

$ Java --version

Now, to change the default Java version using the update-alternatives command as follows:

$ sudo update-alternatives --config java

You will see the following output on your system:

Set default Java version

The list of installed Java versions are presented on the terminal window. The prompt will display on the terminal that will ask you to enter the choice number which Java version you want to set as default.  Enter the number which you want to keep as a default Java version and press Enter. After setting that you can check the default Java version set on your system.

Install Java default JRE

JRE is also known as the Java Runtime Environment. It helps to run almost all Java applications on your system. JRE is mostly included in the Java JDK package. So, if you want to install only JRE on your system then using the following command you can install it on Ubuntu 20.04:

$ sudo apt install default-jre

Or

$ sudo apt install openjdk-11-jre

After executing the above command, you will see the following output on your terminal window:

Install java JRE on Linux

Java has been successfully installed on your system. Now, you can install and run the Java applications on your system.

You have learned how to install Java JDK and JRE on your Ubuntu 20.04 system using the terminal. Moreover, you also learned how to set the default Java version on your system.

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