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Wednesday, 22 January 2020

How to Install Java Runtime Environment on CentOS 8

How to Install Java Runtime Environment on CentOS 8

In this article, you will learn how to install Java runtime environment on CentOS 8.

Java is a general purpose and object-oriented programming language. Java applications are compiled into Byte code and it only requires a Java Virtual Machine (JVM) to execute regardless of the computer architecture. That makes applications platform independent.

Effective Java by Addison-Wesley Professional is a good book, if you want to learn this programming language.

 

Table of Contents:

How to Install Java Runtime Environment on CentOS 8


Environment Specification:

We are using a virtual machine with minimally installed CentOS 8 server.

  • CPU - 3.4 Ghz (2 cores)
  • Memory - 2 GB
  • Storage - 20 GB
  • Operating System - CentOS Linux 8
  • Hostname – java-01.sysadminlabs.com
  • IP Address - 192.168.116.206 /24

 

Installing OpenJDK on CentOS 8:

OpenJDK is the free and open source implementation of Java Platform, Standard Edition (SE) and it is distributed under GNU GPL v2 license.

Two versions of OpenJDK are available in CentOS 8 standard yum repositories. i.e. OpenJDK 8 and OpenJDK 11. Obviously, they are the open source implementations of Oracle Java SE 8 and Oracle Java SE 11.

The installation steps are same for both versions. Here, we are installing OpenJDK 8 on our Linux server, but you can also install OpenJDK 11 by following the same steps.

Connect with java-01.sysadminlabs.com as root user by using a ssh client and install OpenJDK java runtime environment.

# dnf install -y java-1.8.0-openjdk.x86_64

We have installed OpenJDK Java Runtime Environment (JRE). Similarly, we can also install Java Development Kit (JDK) by installing package java-1.8.0-openjdk-devel.x86_64.

Define JAVA_PATH environment variable in /etc/profile file, so it can be set automatically when a login shell is initialized.

# echo "export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-2.el8_1.x86_64" >> /etc/profile

Also set the JAVA_PATH for the current shell.

# export JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-2.el8_1.x86_64

Verify Java version.

# java -version
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)

OpenJDK Java runtime environment has been installed on CentOS 8.

 

Installing Oracle Java on CentOS 8:

Oracle Java is the proprietary distribution of Java platform. Oracle Java is available in Standard (SE), Enterprise (EE) and Micro Editions (ME).

Oracle Java SE is the default choice for most of the environments. Here, we are also installing the Oracle Java 13 SE, that is recently released.

Oracle Java SE 13 is available to download at Oracle website.

You are required to have an Oracle User Account for downloading Oracle Java SE 13 RPM. Therefore, Sign up for a free Oracle User Account, then Sign in to Oracle website by using it.

Transfer the downloaded file to java-01.sysadminlabs.com by using WinSCP.

Connect to java-01.sysadminlabs.com as root user by using a ssh tool such as PuTTY.

You can install Oracle Java SE 13 by using dnf command.

# dnf install -y jdk-13.0.2_linux-x64_bin.rpm

Define JAVA_PATH environment variable in /etc/profile file, so it can be automatically set when a login shell is initialized.

# echo "export JAVA_HOME=/usr/java/jdk-13.0.2" >> /etc/profile

Also set the JAVA_PATH for the current shell.

# export JAVA_HOME=/usr/java/jdk-13.0.2

Verify Java version.

# java -version
java version "13.0.2" 2020-01-14
Java(TM) SE Runtime Environment (build 13.0.2+8)
Java HotSpot(TM) 64-Bit Server VM (build 13.0.2+8, mixed mode, sharing)

We have successfully installed Oracle Java SE 13 on Linux server.

 

Installing Multiple Java Runtime Environments:

We have installed OpenJDK Java 8 and Oracle Java SE 13 on the same Linux server.

Both of these Java versions are available on the CentOS 8 server, but only one is set as default java runtime environment.

Since, we have installed Oracle Java SE 13 after OpenJDK 8. Therefore, we are now running the Oracle Java SE 13 as default java runtime environment.

To switch to OpenJDK 8, we can use the alternatives command.

# alternatives --config java

There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           java-1.8.0-openjdk.x86_64 (/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-2.el8_1.x86_64/jre/bin/java)
*+ 2           /usr/java/jdk-13.0.2/bin/java

Enter to keep the current selection[+], or type selection number: 1

We have set the OpenJDK 8 as default Java runtime environment.

Verify the version of Java now.

# java -version
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)

You can see that, OpenJDK 8 has been set as our default Java runtime environment.

Installation of Java runtime environment on CentOS 8 has been completed successfully.

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