Step 1: Download the latest JDK and Tomcat (in this article, I am using JDK 9 and Tomcat 9).

Step 2: Change the permissions and ownership of the "opt" directory.

user@group:~$ chown username:groupname /opt -R
user@group:~$ chmod 755 /opt -R

Step 3: Now unzip the JDK and Tomcat zip files and copy them to the "opt" directory.

 user@group:~$ cp Downloads/jdk-9.0.1 -Rf /opt/
 user@group:~$ cp Downloads/apache-tomcat-9.0.1 -Rf /opt/tomcat-9

Step 4: Now we need to add some lines to the bottom of the "bashrc" file. To open the "bashrc" file:

 user@group:~$ vim .bashrc

Then press "i" to enable insert mode.

Now add these lines to end of "bashrc":

export CATALINA_HOME=/path/of/tomcat
export CATALINA_OPTS="-Xms256m -Xmx512m -XX:MaxPermSize=128m" 
export MAVEN_OPTS="-Xms256m -Xmx512m" 
export JAVA_HOME=/path/of/jdk 
export JDK_HOME=/path/of/jdk
export IDEA_JDK=/path/of/jdk
export M2_HOME=/path/of/maven 
export PATH=${JAVA_HOME}/bin:${M2_HOME}/bin:${PATH}

After adding the lines, press "Esc" to enable read-only mode. After that, press "Shift + ;" and type "wq" to save the "bashrc" file.

Then, run the following command to set the source of the "bashrc" file:

 user@group:~$ source .bashrc

To check the Java version:

 user@group:~$ java ­-version 

It will show results like so:

Java version "9.0.1" 
Java(TM) SE Runtime Environment (build 9.0.1+11) 
Java HotSpot(TM) 64­Bit Server VM (build 9.0.1+11, mixed mode)

Now start the Tomcat server by running the following command:

 user@group:~$ /path/to/tomcat/bin/startup.sh 

Note: “user@group:~$” is your system default. Don't need to copy it.