Upgrade may cause problems , so its better to do a fresh install.

Completely remove Open-jdk

just use this simple commands in terminal to remove open jdk completely

sudo apt-get purge openjdk-\*

How to install Oracle-Java

To get an automatically update-able Java from Oracle, you can you use the PPA provided from webup8.

sudo add-apt-repository ppa:webupd8team/java
sudo apt-get update
sudo apt-get install oracle-java7-installer

Installing Oracle Java manually

For installing Latest Oracle Java:

To check ubuntu system architecture installed

$ uname -m

or

$ arch

Download the Oracle Java JDK for Linux. Make sure you select the correct compressed binaries for your system architecture 32-bit or 64-bit (which end in tar.gz).It will be downloaded in Downloads folder in home.So first open nautilus with sudo as

sudo nautilus 

and make a folder java under

/usr/local/

and then folow the following commands:

cd /home/"your_user_name"/Downloads
sudo cp -r jdk-7u40-linux-x64.tar.gz /usr/local/java
cd /usr/local/java
sudo chmod a+x jdk-7u40-linux-x64.tar.gz
sudo tar xvzf jdk-7u40-linux-x64.tar.gz

At this point you should have two uncompressed binary directories in /usr/local/java check it by

ls -a

Now edit the system path file by

sudo gedit /etc/profile

scroll down to the last and add following lines

JAVA_HOME=/usr/local/java/jdk1.7.0_40
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export PATH

Save and exit and write these commands in terminal to Inform your Ubuntu Linux system where your Oracle Java JDK/JRE is located.

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.7.0_40/bin/java" 1
sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.7.0_40/bin/javac" 1
sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.7.0_40/bin/javaws" 1
sudo update-alternatives --set java /usr/local/java/jdk1.7.0_40/bin/java
sudo update-alternatives --set javac /usr/local/java/jdk1.7.0_40/bin/javac
sudo update-alternatives --set javaws /usr/local/java/jdk1.7.0_40/bin/javaws
. /etc/profile

Now everything is installed just check it by

java -version

the output must be like

java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b40)
Java HotSpot(TM) Server VM (build 23.1-b03, mixed mode)

Congratulation now its installed.

That may be an OpenJDK issue. Sometimes the Oracle JDK is required in order to get something to work.

Generally the JDKs are downwards compatible, you could as well use version 8.

Here is a tutorial how to install it: http://docs.oracle.com/javase/8/docs/technotes/guides/install/linux_jdk.html

If you already installed (read: put it somewhere on your drive) the Oracle JDK, you can choose it with

update-alternatives --config java

I had problems with that before, if the JDK you want isn't listed, you have to add it to update-alternatives first:

sudo update-alternatives --install /usr/bin/java java /path/to/your/jdk/bin 1

Replace /path/to/your with your path.