To uninstall & install java & jdk,jre

01.Goto directory
sudo nano /etc/environment

02.Add inputs at the end of the line and separate directories with colon:
:/usr/lib/jvm/jdk[version]/bin:/usr/lib/jvm/jdk[version]/db/bin:/usr/lib/jvm/jdk[version]/jre/bin


sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk[version]/bin/java" 0
sudo update-alternatives --install "/usr/bin/java" "javac" "/usr/lib/jvm/jdk[version]/bin/javac" 0
sudo update-alternatives --set java /usr/lib/jvm/jdk/[version]/bin/java
sudo update-alternatives --set java /usr/lib/jvm/jdk[version]/bin/javac

To uninstall JAVA

sudo update-alternatives --remove "java" "/usr/lib/jvm/jdk[version]/bin/java"
sudo update-alternatives --remove "javac" "/usr/lib/jvm/jdk[version]/bin/javac"
sudo update-alternatives --remove "javaws" "/usr/lib/jvm/jdk[version]/jre/bin/javaws"

03.Remove The Package

sudo rm -r /usr/lib/jvm/jdk[version]

04.Uninstall Openjdk

sudo apt-get remove openjdk*

05.Dependencies Remove

sudo apt-get remove --auto-remove openjdk*

06.Remove Openjdk Files And It's Configuration Files

sudo apt-get purge openjdk*

07.Remove Openjdk Along With Dependencies And It's Configuration Files

sudo apt-get purge --auto-remove openjdk*


sudo update-alternatives --config java