Java is one of the most popular programming languages used to build different types of applications and systems.
In this tutorial, we will explain how to install one or more Java (OpenJDK) versions on CentOS 8 and how to set the default Java via alternatives.
Installing OpenJDK 11 on CentOS
01- To install the OpenJDK 11 on CentOS 8, run the following command as root or user with sudo privileges:
$ sudo dnf install java-11-openjdk
02- Once the installation is complete, you can verify it by checking the Java version:
$ java -version openjdk version "11.0.7" 2020-04-14 LTS OpenJDK Runtime Environment 18.9 (build 11.0.7+10-LTS) OpenJDK 64-Bit Server VM 18.9 (build 11.0.7+10-LTS, mixed mode, sharing)
Installing OpenJDK 8 on CentOS
01- If your application requires Java 8, so, you can install it by excuting the below command:
$ sudo dnf install java-1.8.0-openjdk
02- Once the installation is complete, you can verify it by checking the Java version:
$ java -version openjdk version "1.8.0_252" OpenJDK Runtime Environment (build 1.8.0_252-b09) OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)
Setting the Default Java Version
So, if you installed multiple Java versions on your CentOS system, you can use the alternatives command to set which Java version will be used by default.
01- To check what Java version is set as the default one, type:
$ java -version
02- If you want to change the default version, use the command alternatives to list all the installed Java versions.
$ alternatives --config java There are 2 programs which provide 'java'. Selection Command ----------------------------------------------- 1 java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-11.0.7.10-1.el8_1.x86_64/bin/java) *+ 2 java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el8_1.x86_64/jre/bin/java) Enter to keep the current selection[+], or type selection number:
03- Finally, enter the number of the Java version you want to use as the default and press Enter
Setting the JAVA_HOME Environment Variable
The JAVA_HOME environment variable is used by some Java applications to determine the Java installation location and specify which Java version should be used to run the application.
01- To set the JAVA_HOME variable, you can add a script inside the /etc/profile.d directory as below:
JAVA_HOME="/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el8_1.x86_64"
02- Now, load the new environment variables by typing:
$ source /etc/profile.d/java.sh
03- Finally, verify that the JAVA_HOME environment variable was correctly set:
$ echo $JAVA_HOME /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.252.b09-2.el8_1.x86_64
Conclusion
You have successfully installed Java8 and Java 11 on your CentOS 8. You might want to check the following guides:
We hope this tutorial was enough Helpful. If you need more information, or have any questions, just comment below and we will be glad to assist you!
