Stop running server

1) Find running process number 

ps -ef | grep java

2) Kill running server 

ex- sudo kill -9 (processor number)

How to completely uninstall Java?

1) Remove all the Java related packages (Sun, Oracle, OpenJDK, IcedTea plugins, GIJ):

dpkg-query -W -f='${binary:Package}\n' | grep -E -e '^(ia32-)?(sun|oracle)-java' -e '^openjdk-' -e '^icedtea' -e '^(default|gcj)-j(re|dk)' -e '^gcj-(.*)-j(re|dk)' -e '^java-common' | xargs sudo apt-get -y remove sudo apt-get -y autoremove

2) Purge config files:

dpkg -l | grep ^rc | awk '{print($2)}' | xargs sudo apt-get -y purge

3) Remove Java config and cache directory:

sudo bash -c 'ls -d /home/*/.java' | xargs sudo rm -rf

4) Remove manually installed JVMs:

sudo rm -rf /usr/lib/jvm/*

5) Remove Java entries, if there is still any, from the alternatives:

for g in ControlPanel java java_vm javaws jcontrol jexec keytool mozilla-javaplugin.so orbd pack200 policytool rmid rmiregistry servertool tnameserv unpack200 appletviewer apt extcheck HtmlConverter idlj jar jarsigner javac javadoc javah javap jconsole jdb jhat jinfo jmap jps jrunscript jsadebugd jstack jstat jstatd native2ascii rmic schemagen serialver wsgen wsimport xjc xulrunner-1.9-javaplugin.so; do sudo update-alternatives --remove-all $g; done

6) Search for possible remaining Java directories:

sudo updatedb sudo locate -b '\pack200'

Check for java is removed 

java -version

Install Java 

1) sudo apt-get update 

2) sudo apt-get install oracle-java8-installer  

On completion of java installation,one could verify the installed version by & should be 1.8v:-

# java -version 

Check if java is installed 

java -version 

You should see this below message:- 

java version "1.8.0_77"

Java(TM) SE Runtime Environment (build 1.8.0_77-b03)

Java HotSpot(TM) 64-Bit Server VM (build 25.77-b03, mixed mode)

dpkg-query -W -f='${binary:Package}\n' | grep -E -e '^(ia32-)?(sun|oracle)-java' -e '^openjdk-' -e '^icedtea' -e '^(default|gcj)-j(re|dk)' -e '^gcj-(.*)-j(re|dk)' -e '^java-common' | xargs sudo apt-get -y remove sudo apt-get -y autoremove