Replacing OpenJDK with Oracle JDK in Ubuntu

You can completely remove the OpenJDK and fresh Install Oracle Java JDK by the following steps:

1. Remove OpenJDK completely by this command:
   

   sudo apt-get purge openjdk-\*

2. Download the Oracle Java JDK here.
   Note: download appropriate file, for example if your system is x64 Ubuntu (i.e, Debian) the download file is named like this: jdk-8u51-linux-x64.tar.gz
   To find which version is your OS, check here
3. Create a folder named java in /usr/local/by this command:
   

   sudo mkdir -p /usr/local/java

4. Copy the Downloaded file in the directory /usr/local/java. To do this, cd into directory where downloaded file is located and use this command for copying that file to /usr/local/java/:
   

   sudo cp -r jdk-8u51-linux-x64.tar.gz /usr/local/java/

5. CD into /usr/local/java/ directory and extract that copied file by using this command:
   

   sudo tar xvzf jdk-8u51-linux-x64.tar.gz

6. After extraction you must see a folder named jdk1.8.0_51.
7. Update PATH file by opening /etc/profile file by the command sudo nano /etc/profile and paste the following at the end of the file:
   

   JAVA_HOME=/usr/local/java/jdk1.8.0_51
   PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
   export JAVA_HOME
   export PATH

8. Save and exit.
9. Tell the system that the new Oracle Java version is available by the following commands:
   

   sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.8.0_51/bin/java" 1
   sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.8.0_51/bin/javac" 1
   sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.8.0_51/bin/javaws" 1

10. Make Oracle Java JDK as default by this following commands:
    

    sudo update-alternatives --set java /usr/local/java/jdk1.8.0_51/bin/java
    sudo update-alternatives --set javac /usr/local/java/jdk1.8.0_51/bin/javac
    sudo update-alternatives --set javaws /usr/local/java/jdk1.8.0_51/bin/javaws

11. Reload sytem wide PATH /etc/profile by this command:
    

    source /etc/profile

12. Reboot your system.
13. Check Java JDK version by java -version command . If installation is succesful, it will display like the following:
    

    java version "1.8.0_51"
    Java(TM) SE Runtime Environment (build 1.8.0_51-xxx)
    Java HotSpot(TM) Server VM (build 25.51-xxx, mixed mode)

That's it!
Note: We Assumed that the downloaded file is named jdk-8u51-linux-x64.tar.gz and used this name in all the commands used in steps 2, 4 and 5. It may depends on the type of O.S, processor type (i.e., 32bit or 64bit)

Source: Stackoverflow.com
Reproduced here so that I don't have to find it again, I can simply refer back to my this blog.