Check if Java is already installed
$ java -version
If you see an output like below then Java is already installed on your machine so skip the next step.
java version "1.7.0_55"
Java(TM) SE Runtime Environment (build 1.7.0_55-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.55-b03, mixed mode)
If you don't see the output like above then you need to install Java on your system. Please download the OS X version from the Oracle website.
Check if Java is correctly installed by running the java -version command again.
Add JAVA_HOME to your environment variables by adding the line below to your env.sh.
export JAVA_HOME="`/usr/libexec/java_home -v 1.7`"
You should have JAVA working now. If you use Eclipse as your Java IDE it'll prompt you to install Java 6, go ahead and click Ok.