How to Set JAVA_HOME / PATH variables Under Linux

After installing Java Development Kit on Linux/Unix, you may still need to do some configuration to get Java ready for running or compiling Java programs. The following instruction will guide you through the process of setting up JDK for software development.

In Linux, ~/.bash_profile is a startup script which generally runs once. This particular file is used for commands which run when the normal user logs in. Common uses for .bash_profile are to set environment variables such as PATH, JAVA_HOME, to create aliases for shell commands, and to set the default permissions for newly created files.

Set JAVA_HOME / PATH for single user

Login to your account and open .bash_profile file
$ cd $HOME
$ vi ~/.bash_profile

Set PATH and JAVA_HOME as follows:
 
PATH=$PATH:$HOME/bin:/usr/jdk1.6.0_30/bin
JAVA_HOME=/usr/jdk1.6.0_30

Note: Don't delete the previous PATH, Just append the jdk path after : like "/usr/jdk1.6.0_30/bin" as above .

export PATH
export JAVA_HOME

Save and close the file. Just logout and login back to see new changes:
$ echo $JAVA_HOME
$ echo $PATH

Tip: Use the following command to find out exact path to which java executable under UNIX / Linux:
$ which java

How to set JAVA PATH on Windows