How To Install Java on Ubuntu with Apt-Get & OEL ,RHEL with yum or manually

sudo apt-get update

java -version

To install OpenJDK 7, execute the following command:

sudo apt-get install openjdk-7-jre

sudo yum install openjdk-7-jdk

sudo apt-get install oracle-java6-installer

sudo apt-get install oracle-java7-installer

sudo apt-get install oracle-java8-installer

sudo update-alternatives --config java

It will usually return something like this if you have 2 installations

There are 2 choices for the alternative java (providing /usr/bin/java).

Selection    Path                                            Priority   Status

------------------------------------------------------------

* 0            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      auto mode

  1            /usr/lib/jvm/java-6-openjdk-amd64/jre/bin/java   1061      manual mode

  2            /usr/lib/jvm/java-7-oracle/jre/bin/java          1062      manual mode

Or download setup from oracle site and install java & configure manually

To set the JAVA_HOME environment variable

Set the path of the Java 

Run in terminal 

# alternatives --install /usr/bin/java java /jdk1.6/bin/java 120    

Note :"jdk1.6/bin/java 120" location of java installed folder, if installed java manually .

# alternatives  --config java

Edit the basj profile:- 

   cd ~

   vi .bash_profile

   JAVA_HOME=/jdk1.6/bin/java

   export PATH JAVA_HOME

   source .bash_profile

Exit command

:wq!

Done .Verify 

# java -version

# which java