Installing Oracle JDK in Ubuntu

1. Installing Java.

Things you need to know.

a) JDK - Java Development Kit. (Usually contains one ore more JRE with it)
    JRE - Java Runtime Environment.

b) x86 is for a 32-bit OS, and x64 is for a 64-bit OS

1.1 Download the JDK from http://www.oracle.com/technetwork/java/javase/downloads/index.html.

1.2 Uncompress the file.

Command:

tar -xvf jdk-7u40-linux-x64.tar.gz

The above command installs the JDK in the current path.

1.3 Next task is to put the JDK in usr/lib path.

For this create a dir in /usr/lib/jvm

$ sudo mkdir -p /usr/lib/jvm

Change the directory of the current install

$ sudo mv ./jdk1.7.0_40 /usr/lib/jvm/jdk1.7.0_40


1.4 Run the following commands:
$ sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk1.7.0_40/bin/java" 1
$ sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk1.7.0_40/bin/javac" 1

The above commands set the priority for the current install as 1.


1.5 Alter the ownership and permissions of the executables by running the following commands.

$ sudo chmod a+x /usr/bin/java

$ sudo chmod a+x /usr/bin/javac 
$ sudo chmod a+x /usr/bin/javaws
$ sudo chown -R root:root /usr/lib/jvm/jdk1.7.0_40

Now check the java version
$java -version


You must get something like this:

sony@ubuntu:~/Downloads$ java -version
java version "1.7.0_40"
Java(TM) SE Runtime Environment (build 1.7.0_40-b43)
Java HotSpot(TM) 64-Bit Server VM (build 24.0-b56, mixed mode)

For more instructions checkout --
http://www.oracle.com/technetwork/java/javase/