Setting up java in linux

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

                                                          Command :  java -version 

If java is already present in your system then you will see something like the below

                                   Java HotSpot(TM) Server VM (build 23.6-b04, mixed mode)

 

If you don't have java installed then you can install it by following this post

-> Download the Oracle Java JDK/JRE for Linux from here.

    Make sure you select the correct compressed binaries for your system architecture 32-bit or 64-bit  

    (which end in tar.gz).

-> Copy the Oracle Java binaries into 

                                                 /usr/local/java directory

     In most cases, the Oracle Java binaries are downloaded to:

                                                /home/"your_user_name"/Downloads

-> Once you have downloaded , the next step is to install it. The following lines will guide you in the  installation process.

Installation instructions for 32-bit Oracle Java on 32-bit Ubuntu Linux     

Type the following commands in the terminal

1. Command to traverse to the location where you have downloaded the Oracle java binaries

cd /home/"your_user_name"/Downloads  

2. Command to copy the downloaded jdk into an appropriate location for easy installation and configuration

sudo cp -r jdk-7u21-linux-i586.tar.gz /usr/local/java  

3. Command to copy the downloaded jre into an appropriate location for easy installation and configuration 

  

sudo cp -r jre-7u21-linux-i586.tar.gz /usr/local/java

4. Now traverse to the directory where you have copied the jre and jdk by typing the following command. 

cd /usr/local/java

Installation instructions for 64-bit Oracle Java on 64-bit Ubuntu Linux
Type the following commands in the terminal

1. Command to traverse to the location where you have downloaded the Oracle java binaries

cd /home/"your_user_name"/Downloads  

2. Command to copy the downloaded jdk into an appropriate location for easy installation and configuration

sudo cp -r jdk-7u21-linux-x64.tar.gz /usr/local/java  

3. Command to copy the downloaded jre into an appropriate location for easy installation and configuration 

  

sudo cp -r jre-7u21-linux-x64.tar.gz /usr/local/java

4. Now traverse to the directory where you have copied the jre and jdk by typing the following command. 

cd /usr/local/java

The next step is to Unpack the compressed Java binaries, in the directory /usr/local/java

For 32-bit : Type the following commands

sudo tar xvzf jdk-7u21-linux-i586.tar.gz 

sudo tar xvzf jre-7u21-linux-i586.tar.gz

For 64-bit : Type the following commands

 sudo tar xvzf jdk-7u21-linux-x64.tar.gz 

sudo tar xvzf jre-7u21-linux-x64.tar.gz

By now, you should have two uncompressed binary directories in /usr/local/java for the Java JDK/JRE

Type ls -a to check it  , it should display as shown below

jdk1.7.0_21  

jre1.7.0_21

Now Edit the system PATH file /etc/profile and add the following system variables to your system path. 

note:- you can use nano, gedit or any other text editor, as root, open up /etc/profile. 

For gedit: Type the following command

sudo gedit /etc/profile

For nano: Type the following command

sudo nano /etc/profile

Scroll down to the end of the file using your arrow keys and add the following lines to the end of your /etc/profile file:

JAVA_HOME=/usr/local/java/jdk1.7.0_21 

PATH=$PATH:$HOME/bin:$JAVA_HOME/bin

JRE_HOME=/usr/local/java/jre1.7.0_21 

PATH=$PATH:$HOME/bin:$JRE_HOME/bin

export JAVA_HOME

export JRE_HOME

export PATH

Save the /etc/profile file and exit. 

Reload your system wide PATH /etc/profile by typing the following command:

. /etc/profile

leave your doubts or suggestions in comments section..