How to Install Oracle JDK 8 Ubuntu 18.10 Cosmic

Ubuntu Cosmic Oracle JDK 8 - Setup

4. Next Relocate JDK 8.

   sudo su

   If Got “User is Not in Sudoers file” then see: How to Enable sudo
   Make a jvm Directory if Not already there with

   if [ ! -d "/usr/lib/jvm" ]; then mkdir /usr/lib/jvm; fi

   Set the root superUser as owner

   sudo chown -R root:root /tmp/jdk1.8*

   Reiterate the Execution Permission over the Java binaries

   chmod -R +x /tmp/jdk1.8*/bin

   Finally, Shift the Java contents with

   mv /tmp/jdk1.8* /usr/lib/jvm/
   

5. Installing Oracle Java JDK 8
   You can directly Copy & Paste the Commands into Terminal..

   update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.8*/bin/java 1065
   

   update-alternatives --install /usr/bin/javac javac /usr/lib/jvm/jdk1.8*/bin/javac 1065
   

   update-alternatives --install /usr/bin/jar jar /usr/lib/jvm/jdk1.8*/bin/jar 1065
   

   update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.8*/bin/javaws 1065
   

   Checking or Setting the System Java Version in Use with

   update-alternatives --config java
   

   To Switch of Java Version Just Enter the Selection Number on First, Column. :)