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Installing Java on Ubuntu


The Java Technology is both a programming language and a platform [1]. The java platform is one on top of which java programs run and it can be described as a software-only platform that runs on top of other hardware based platforms. The Java platform consists of these two major components [2].
  • The Java Virtual Machine
  • The Java Application Programming Interface (API)

The importance of installing java on your local machine is due to the reason that many web and  desktop applications may be partially or fully dependent on the java run-time. Therefore it is essential to install a version of java into your local machine.

This tutorial guides you through a simple mechanism to install java on the Ubuntu platform.


1. First open up a terminal in your Ubuntu environment

2. Update the existing packaging index by entering the following command in the terminal


$ sudo apt-get update                                                     


3. Check if java is available with the following command. If it is available you do not need to install it again.

$ java -version                                                           
4. If not available then install java to your ubuntu environment using the following command. This will install the official JDK which is the one distributed by Oracle.

$ sudo apt-get install oracle-java7-installer                         
or

$sudo apt-get install oracle-java8-installer                          

You can select either one of the above depending on the java version that you want to install.

 Please note that some applications have not yet been migrated or have not been developed to use the latest java release which is java8. Therefore when determining the version please consider the above or the program may fail to run.



5. Ideally the installed version on java should reside in /usr/lib/jvm directory. If you are unable to locate it there then enter the following command in your terminal and you should be able to locate the installation directory of java. 


$ whereis java                                                                                                                         


6. Now java is installed. nest we need to add the java path to the existing classpath. Therefore we need to set the $JAVA_HOME environment variable. In order to set this variable we need to navigate to the home directory and edit the .bashrc file.


$ cd /home/shenavi                                             
(note that /home/shenavi is my home folder)


shenavi@shenavidemel:~$ sudo vi .bashrc                                                                            

7. You can also open this file using any other text editor with the admin user. (using the sudo command). After opening it navigate to the bottom of the file and add the following two lines at the end where /usr/lib/jvm/java-7-oracle is the installation directory of java. If the installation directory differs from this replace that in the java home below.


export JAVA_HOME=/usr/lib/jvm/java-7-oracle                                                                  
export PATH=${JAVA_HOME}/bin:${PATH}                                                                   
8. After this change save changes and close. Now java is successfully installed in your machine. To check the installation you can go to your terminal and enter the command mention in step 3.

 Or you can simply type java or javac in the terminal and observe the possible options to use with the newly installed java. Which means you have now successfully installed java on your Ubuntu platform.




References

[1] https://www.java.com/en/download/faq/whatis_java.xml

[2] http://docs.oracle.com/javase/tutorial/getStarted/intro/definition.html
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