This tutorial helps you to install Java 9 or update Java on your system i.e. CentOS 7 / RHEL platform. In our previous article we discussed Java 8 installation on CentOS 7 and Java 8 installation with Ansible.

Step 1 – Download Latest Java Archive (Java 9)

Download latest Java SE Development Kit 9 release from its official download page Use following commands to download.

root@devopstechie$ cd /opt/
root@devopstechie$ wget --no-cookies --no-check-certificate --header "Cookie: gpw_e24=http%3A%2F%2Fwww.oracle.com%2F; oraclelicense=accept-securebackup-cookie" "http://download.oracle.com/otn-pub/java/jdk/8u151-b12/e758a0de34e24606bca991d704f6dcbf/jdk-8u151-linux-x64.tar.gz"
root@devopstechie$ tar xzf jdk-9.0.4_linux-x64_bin.tar.gz

Step 2 – Install Java 9 with Alternatives

After extracting archive file use alternatives command to install it.

root@devopstechie$ cd /opt/jdk-9.0.4/
root@devopstechie$ alternatives --install /usr/bin/java java /opt/jdk-9.0.4/bin/java 2
root@devopstechie$ alternatives --config java


There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*  1           /opt/jdk1.8.0_151/bin/java
 + 2           /opt/jdk-9.0.4/bin/java

Enter to keep the current selection[+], or type selection number: 2

Up till now JAVA 9 has been successfully installed on your system. We also recommend to setup javac and jar commands path using alternatives

root@devopstechie$ alternatives --install /usr/bin/jar jar /opt/jdk-9.0.4/bin/jar 2
root@devopstechie$ alternatives --install /usr/bin/javac javac /opt/jdk-9.0.4/bin/javac 2
root@devopstechie$ alternatives --set jar /opt/jdk-9.0.4/bin/jar
root@devopstechie$ alternatives --set javac /opt/jdk-9.0.4/bin/javac

Step 3 – Check Installed Java 9 Version

Check the installed Java version on your system using following command.

root@devopstechie$ java -version

java version "9.0.4"
Java(TM) SE Runtime Environment (build 9+181)
Java HotSpot(TM) 64-Bit Server VM (build 9+181, mixed mode)

Step 4 – Setup Java 9 Environment Variables

Set the Java environment variables using following commands. Setup JAVA_HOME, JRE_HOME and PATH environment variables

root@devopstechie$ export JAVA_HOME=/opt/jdk-9.0.4
root@devopstechie$ export JRE_HOME=/opt/jdk-9.0.4/jre
root@devopstechie$ export PATH=$PATH:/opt/jdk-9.0.4/bin:/opt/jdk-9.0.4/jre/bin

Also you can put all above environment variables in /etc/environment file for auto loading on system boot.
References:
https://tecadmin.net/install-java-9-centos-fedora/