Install OpenJDK on Ubuntu Server
This article is for those looking for a detailed and straightforward guide on installing OpenJDK on Ubuntu Server.
With the release of Java 11, Oracle JDK became commercial and is no longer free.
OpenJDK is an open-source implementation of the Java Standard Edition platform with contributions from Oracle and the Java open community. The Oracle JDK build process is built from the OpenJDK source, so there isn’t much difference between Oracle JDK and OpenJDK.
OpenJDK is free but will need to be updated every 6 months.
In this guide, we will consider the case when you already have a server with the Ubuntu Server 20.04 LTS operating system installed on it.
You can read more about how to install Ubuntu Server 20.04 LTS in my guide “Install Ubuntu Server 20.04 LTS”.
In addition, OpenSSH must be installed on the server, and port 22 must be open in order to be able to connect to the server using the SSH protocol.
To install OpenSSH on a server, you can use the command:
sudo apt install openssh-serverThis guide describes how to connect to a server using the iTerm2 terminal emulator installed on the macOS operating system.
We connect to the server on which you plan to install OpenJDK.
Update the local package index to the latest changes in the repositories using the command:
sudo apt update
You may need a Java Development Kit (JDK) in addition to the JRE in order to compile and run certain Java-based software.
To install the JDK, run the following command, which will also install the JRE:
sudo apt-get install -y default-jdk
Now you need to make sure that OpenJDK is installed correctly. To do this, you need to run the command:
java -version
Based on the message received, OpenJDK is installed correctly.
Many programs written with Java use the “JAVA_HOME” environment variable to determine where Java is installed. Therefore, you need to define this variable and assign it a value containing the path to the Java installation location.
Let’s define the path to the Java installation location using the command:
sudo update-alternatives --config java
In this example, the path to the Java installation location looks like this:
/usr/lib/jvm/java-11-openjdk-amd64/bin/In order to define an environment variable and assign a value to it, you need to make changes to the “environment” file by opening it in a text editor using the command:
sudo vim /etc/environment
Press the “i” button to switch to edit mode, then at the end of the file define a new variable “JAVA_HOME” and assign it a value containing the path to the Java installation location obtained earlier.
JAVA_HOME="/usr/lib/jvm/java-11-openjdk-amd64/bin/"Please note that the path to the Java installation location must be specified up to and including the “bin” folder.
Now press the “Esc” button to exit edit mode, then type “:x” and press the “Enter” button to save your changes and exit the editor.
Next, you need to apply the changes made to the current session using the command:
source /etc/environment
Now let’s make sure that the environment variable has the correct value using the command:
echo $JAVA_HOME
Based on the message received, the environment variable has the correct value.
