Update README.md file

Author: chrishantha

README.md

@@ -1,4 +1,54 @@
-install-java
-============
+Oracle Java installation script for Linux
+=========================================
 
-Installation script for setting up Java on Linux
+"install-java.sh" is an installation script for setting up Oracle Java Development Kit on Linux.
+
+I'm mainly using Ubuntu and therefore this script is tested only on Ubuntu 14.04 64-bit version
+
+## Prerequisites
+
+This script will not download Java distribution. You need to [download JDK] from Oracle. 
+
+Only requirement is to have all required distributions in a single directory.
+
+For example, if you want to install Java 7, following files must be downloaded.
+
+ - jdk-7u72-linux-x64.tar.gz
+ - jdk-7u72-linux-x64-demos.tar.gz
+ - UnlimitedJCEPolicyJDK7.zip
+
+Similarly for Java 8, following are the files required
+
+ - jdk-8u25-linux-x64.tar.gz
+ - jdk-8u25-linux-x64-demos.tar.gz
+ - jce_policy-8.zip
+
+## Installation
+
+The script needs to be run as root.
+
+You need to provide the JDK distribution file (tar.gz) and the Java Installation Directory. The default value for Java installation directory is "/usr/lib/jvm"
+
+```
+Usage: 
+install_java.sh -f <java_dist> [-p] <java_dir>
+
+-f: The jdk tar.gz file
+-p: Java installation directory
+```
+
+Example: Install Oracle JDK 7
+
+`sudo ./install_java.sh -f ~/Software/jdk-7u72-linux-x64.tar.gz`
+
+Example: Install Oracle JDK 8
+
+`sudo ./install_java.sh -f ~/Software/jdk-8u25-linux-x64.tar.gz`
+
+## License
+
+Copyright (C) 2014 Isuru Perera
+
+Licensed under the Apache License, Version 2.0
+
+[download JDK]: http://www.oracle.com/technetwork/java/javase/downloads/index.html