How to install Java 6 on Ubuntu

In one of the previous post of mine I have shown you how to install Sun(Oracle) Java on Ubuntu through its repository. This will, by default, install Java-7 on your machine as Ubuntu 12.04(and onwards) have Java-7 in their repository. But, sometimes you may come across a situation wherein you need some specific version of Java. For example, it is advisable to use Java-6 while trying to configure or use Apache Hadoop. In such a scenario you need to download the appropriate version of Java and install it manually. It is again a straightforward process. Just follow the steps below :

Note : Java-6 has been taken here, as an example, on a machine running Ubuntu 12.10

Step 1 : Download the required version of Java from the official download page. It will download  jdk-6u38-linux-x64.bin inside your Downloads directory.

Step 2 : Go to the directory where jdk was downloaded(Download here) and make it an executable file using this command :
apache@hadoop:~/Downloads$ sudo chmod +x jdk-6u38-linux-x64.bin

Step 3 : Run this executable .bin file using :
apache@hadoop:~/Downloads$ ./jdk-6u38-linux-x64.bin

Step 4 : Now move the file to the /usr/lib/jvm directory with the help of mv command :
apache@hadoop:~/Downloads$ sudo mv jdk1.6.0_38/ /usr/lib/jvm/

Step 5 : This is the step where you actually do the installation. Use the following commands to do that :
apache@hadoop:~/Downloads$ sudo update-alternatives  --install /usr/bin/javac javac /usr/lib/jvm/jdk1.6.0_38/bin/javac 1
apache@hadoop:~/Downloads$ sudo update-alternatives --install /usr/bin/java java /usr/lib/jvm/jdk1.6.0_38/bin/java 1
apache@hadoop:~/Downloads$ sudo update-alternatives --install /usr/bin/javaws javaws /usr/lib/jvm/jdk1.6.0_38/bin/javaws 1

Once you are done with these steps you are good to go. One step is actually still required though. The above procedure will just install Java-6 on your machine. In case you have multiple versions of Java installed on your machine, you need to set which version you want to use as your default Java. To do so issue the command shown below :
apache@hadoop:~/Downloads$ sudo update-alternatives --config java

This will show you all the Java versions installed on your machine. Choose the number corresponding to the version of your choice and you are all set.