How to install Java 17 On Rocky/Alma Linux 8

In this guide we are going to explore how to install Java Runtime Environment (JRE) and the Java Developer Kit (JDK) in Rocky Linux 8. This guide also works for Centos 8/Rhel 8/Alma Linux 8

Java and the JVM (Java’s virtual machine) are required for many kinds of software, including Tomcat, Jetty, Glassfish, Cassandra and Jenkins.

Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible. Java was developed by Sun Microsystems (which is now the subsidiary of Oracle) in the year 1995. James Gosling is known as the father of Java.

Also Check:

Prerequisites

Up to date Rocky Linux 8/Rhel 8/Alma Linux 8 system
Root access to the server or user with sudo access
Internet access from the server

Table of content

Ensuring that the server is up to date
Installing java
Testing the installation
Toggling multiple Java versions
Configuring the Environmental Variable

Ensuring that the server is up to date

Before proceeding, let us ensure that our server is up to date and all the packages are the latest version. Use these commands to achieve this:

sudo dnf -y update

If there are packages to upgrade, the above comand may take a couple of minutes.

Let us also install some common packages that we might need. I use vim text editor, and wget to download packages please make sure they are installed using this command:

sudo dnf -y install vim wget

Installing Java

Use the following command to check whether java is installed in your sytem.

$ java -version
-bash: java: command not found

If you see java: command not found then it means that java is not installed. If java is installed, that command will print out the java version

The openjdk version available in the default Rocky Linux Repos is not up to date. Get the latest in this https://jdk.java.net/17/

Download with this curl command:

curl -LO https://download.java.net/java/GA/jdk17.0.1/2a2082e5a09d4267845be086888add4f/12/GPL/openjdk-17.0.1_linux-x64_bin.tar.gz

This is the output on my server:

$ curl -LO https://download.java.net/java/GA/jdk17.0.1/2a2082e5a09d4267845be086888add4f/12/GPL/openjdk-17.0.1_linux-x64_bin.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  178M  100  178M    0     0  76.3M      0  0:00:02  0:00:02 --:--:-- 76.3M

The file will be downloaded to the current directory as

openjdk-17.0.1_linux-x64_bin.tar.gz

$ ls
openjdk-17.0.1_linux-x64_bin.tar.gz

Let’s extract the package with tar command

tar -xzf openjdk-17.0.1_linux-x64_bin.tar.gz

Now let us move the content that was extracted to the /opt directory

sudo mv jdk-17.0.1/ /opt

Now that the content is extracted and added to the /opt directory, we need to export Java home so the java apps know where the JDK installation is and to update the path to include executables in the java binary directory. That way we can use the java command without specifying the full path.

Let us set these variables in the .bashrc file. Open the file with your text editor, I am using vim:

vim ~/.bashrc

Now add these lines to set Java home and to include the executables binary directory

export JAVA_HOME=/opt/jdk-17.0.1
export PATH=$PATH:$JAVA_HOME/bin

With those set, you will have to logout then login or reload the login shell using this command:

source ~/.bashrc

Confirm that Java is now working fine by checking for the version:

$ java -version
openjdk version "17.0.1" 2021-10-19
OpenJDK Runtime Environment (build 17.0.1+12-39)
OpenJDK 64-Bit Server VM (build 17.0.1+12-39, mixed mode, sharing)

To verify if the JDK is installed properly, we will check the version of javac, which is the Java compiler.

$ javac -version
javac 17.0.1

Testing the installation

Let us test that Java 17 is installed properly in this step by creating a simple script that prints out Java is installed properly.

Create the directory and switch to it

mkdir simple-app
cd simple-app

I use vim to create and edit text files in my system. Use the text editor of your choice in this step. I will create a file Simple.java using this command:

vim Simple.java

Add these content to the file

public class Simple{
   public static void main(String[] args) {
      System.out.println("Citizix - Java is installed properly");
   }
}

Now that we have created our program, we need to compile the Java source code into bytecode (class file) using the javac compiler.

javac Simple.java

You will get a new file called Simple.class, which is the compiled Java class file.

$ ls
Simple.class  Simple.java

The command above will only compile the Java source code into bytecode. In order to run the program, we run the java command with the name of our class file as an argument.

java Simple

If everything works well, you’ll see a message “Citizix - Java is installed properly” on the screen.

$ java Simple
Citizix - Java is installed properly

Configuring the Environmental Variable

Some Java applications require the JAVA_HOME environmental variable in order to run properly. Some programs are very specific in how they are executed. If JAVA_HOME isn’t set, you’ll get an error. Setting JAVA_HOME will prevent this problem from arising.

To check which Java installations and paths exist, use this command:

$ which java
/opt/jdk-17.0.1/bin/java

In my case, I get the Java installation binary path to be this /opt/jdk-17.0.1/bin/java

We are going to set this path in an enviroment file /etc/environment where all the apps can access.

Open the file with vim:

sudo vim /etc/environment

Now we need to add a line exporting the Java home to the file like this export JAVA_HOME=... making the value to be the path we got for our Java installation:

export JAVA_HOME=/opt/jdk-17.0.1/bin/java

This file will set the JAVA_HOME path of OpenJDK 17 as environmental variables for all users in the system.

To apply the change, run the following command.

source /etc/environment

To verify that the path variable has been applied, run the following command.

echo $JAVA_HOME

The path should be set to the path of OpenJDK 17, which you have copied above. This is the value in my case:

$ echo $JAVA_HOME
/opt/jdk-17.0.1/bin/java

From now on, you don’t have to set the JAVA_HOME path every time when using Java programs. Also, if you want to use other OpenJDK versions instead of 17, adapt the path accordingly.

Conclusion

In this tutorial, you have learned how to install Java 17 on a Rocky Linux 8/Alma Linux 8 system. If you need further information about the Java language, please refer to its official documentation.