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.

I find these "it works on my machine" and "use what I use" answers annoying. If you're using Oracle's JDK and having this problem on Linux, add the following line to your ~/.java/deployment/deployment.properties file:

deployment.security.level=MEDIUM

Then restart your browser. This is the Linux equivalent of all the Windows and Mac OS X specific "set your security level to Medium" instructions polluting the "how do I do this on Linux" search results.

Good luck!