How to install Java 7 and Java 8 in CentOS 7?

Java has three concepts

1. Versions like 1.7 , 1.8 which are also called Java 7 and Java 8
2. Various distributions like JRE, JDK, etc
3. Vendor distributions i.e the Oracle distributes or OpenJDK distributes.

In the Development machine install the JDK which also has the JRE.
In Server machines install only the JRE.
If there is an Open JDK version available for your OS use this else take the Oracle one.
Since there is an OpenJDK version for CentOS we shall install this distribution.

CentOS 7 Server with UI should come pre-installed with Java 7 JRE.

Check if Java is already installed by issuing the following command.

java -version
It should print out

java version "1.7.0_79"

Yum is the package manager in CentOS (Windows installer in Microsoft). It can auto detect if java is already installed and install only if its not.

Install Java 8 (1.8) JDK using the following command. You need to have admin privileges.


sudo yum install java-1.8.0-openjdk-devel.x86_64

If already installed you would get

Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* base: mirror.5ninesolutions.com
* extras: mirror.millry.co
* updates: mirror.cogentco.com
Package 1:java-1.8.0-openjdk-devel-1.8.0.65-2.b17.el7_1.x86_64 already installed and latest version


Check the installation by using the following command. which list any java processes running. This is available only in the JDK version and not on the JRE version

jps


Install Java 8 (1.8) JRE using the following command. You need to have admin privileges.

sudo yum install java-1.8.0-openjdk.x86_64


Don't bother about the naming convention its called openjdk, this is a company name but installs the JRE.

If Java 7 is not installed and you got a server core version of CentOS 7.

Then issue the following  commands before you install Java 8

//install the java 7 JRE
sudo yum install java-1.7.0-openjdk.x86_64

//install the java 7 JDK
sudo yum install java-1.7.0-openjdk-devel.x86_64