How to install Oracle JDK in Ubuntu

This article for those who only want to install the Oracle Java JDK with the Oracle Java JRE included from Oracle website.
The following Instructions for how to install Oracle Java JDK on Debian based Linux operating systems such as Debian, Ubuntu and Linux Mint.

(The Manual Method)

Note: you must replace "jdk1.7.0_51" by your java file version

Step 1: Check to see if your Ubuntu Linux operating system architecture is 32-bit or 64-bit, open up a terminal and run the following command below.

file /sbin/init

Step 2: Check if you have Java installed on your system. To do this, you will have to run the Java version command from terminal.

java -version

If you have OpenJDK installed on your system, you have the wrong vendor version of Java installed for this exercise

Step 3: Completely remove the OpenJDK/JRE from your system if exists

To remove OpenJDK/JRE completely from your system

sudo apt-get purge openjdk-\*

Step 4: Download the Oracle Java JDK for Linux and make sure you select the correct "compressed binaries file" for your system architecture 32-bit or 64-bit (which end with .tar.gz), i.e. "[java-version]-i586.tar.gz" for 32bit and "[java-version]-x64.tar.gz" for 64bit

Step 5: Create a directory to hold your Oracle Java JDK and JRE binaries

sudo mkdir -p /usr/local/java 

Step 6: Move the compressed file to /usr/local/java directory

sudo mv Downloads/jdk-7u51-linux-i586.tar.gz /usr/local/java

Step 7: Move current location to the new directory

cd /usr/local/java

Step 8: Run the following commands on the downloaded Oracle Java tar.gz files. Make sure to do this as root in order to make it executable for all users on your system. To open a root terminal type sudo -s you will be prompted for your logon password.

sudo chmod a+x jdk-7u51-linux-i586.tar.gz

Step 9: Unpack the compressed Java binaries, in the directory /usr/local/java, the remove the compressed file

sudo tar xvzf jdk-7u51-linux-i586.tar.gz
sudo rm -f jdk-7u51-linux-i586.tar.gz

Step 10: Double-check your directories. At this point, you should have only uncompressed binary directory in /usr/local/java for the Java JDK/JRE listed

ls -a

Step 11: Edit the system PATH file /etc/enviroment to add the system variables to your system path. Use nano, gedit or any other text editor, as root, open up /etc/enviroment.

sudo gedit /etc/enviroment

or

sudo nano /etc/enviroment

Step 12: Text Editor will popped up, Scroll down to the end of the file using your arrow keys and add the following lines below to the end of your /etc/enviroment file

JAVA_HOME=/usr/local/java/jdk1.7.0_51
PATH=$PATH:$HOME/bin:$JAVA_HOME/bin
export JAVA_HOME
export PATH

Step 13: Save the /etc/enviroment file and exit

Step 14: Inform your Ubuntu Linux system where is Oracle Java JDK/JRE located.

the following command notifies the system that Oracle Java JRE is available for use

sudo update-alternatives --install "/usr/bin/java" "java" "/usr/local/java/jdk1.7.0_51/bin/java" 1

the following command notifies the system that Oracle Java JDK is available for use

sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/local/java/jdk1.7.0_51/bin/javac" 1

the following command notifies the system that Oracle Java Web start is available for use

sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/local/java/jdk1.7.0_51/bin/javaws" 1

Step 15: Inform your Ubuntu Linux system that Oracle Java JDK/JRE must be the default Java

the following command set the java runtime environment for the system

sudo update-alternatives --set java /usr/local/java/jdk1.7.0_51/bin/java

the following command set the javac compiler for the system

sudo update-alternatives --set javac /usr/local/java/jdk1.7.0_51/bin/javac

the following command set Java Web start for the system

sudo update-alternatives --set javaws /usr/local/java/jdk1.7.0_51/bin/javaws

Step 16: Reload your enviroment variable file "/etc/enviroment" by typing the following command (notice the space after dot):

. /etc/enviroment

Step 17: Test to see if Oracle Java was installed correctly on your system. Run the following commands and note the version of Java:

The following command displays the version of java running on your system

java -version

The following command lets you know that you are now able to compile Java programs from the terminal

javac -version

Note: if you got an error like this

java cannot execute binary file

You need to ensure from version compatibility, because this problem caused when you using a x86 Ubuntu with a x86_64 JDK, you can test your ubuntu version by the following command

uname -i

Step 18: Congratulations, you have comoleted installation steps, Now reboot your Ubuntu Linux system. Afterwards, your system will be fully configured for running and developing Java programs

(The Easy Method)

The easy way to install Oracle JDK using Web Up8 Oracle Java OOS, but the PPA not always up to date, also note that using PPA is not very recommended for safty reason, read more about the dangers of using PPA 

However, is you understand that and you still want to install JDK using PPA just open the terminal and type the following commands
Note: This installs JDK (which includes Java JDK, JRE and the Java browser plugin).

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

--
http://www.wikihow.com/Install-Oracle-Java-JDK-on-Ubuntu-Linux 
http://www.webupd8.org/2012/01/install-oracle-java-jdk-7-in-ubuntu-via.html
http://askubuntu.com/questions/56104/how-can-i-install-sun-oracles-proprietary-java-6-7-jre-or-jdk
http://rootzwiki.com/topic/23008-howto-install-java-7-on-ubuntu-1204/
http://www.liberiangeek.net/2012/04/install-oracle-java-jdk-7-in-ubuntu-12-04-precise-pangolin/