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 "1.8.0_45"
Java(TM) SE Runtime Environment (build 1.8.0_45-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.45-b02, 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 1.8`"
You should have JAVA working now. You can use Eclipse or IntelliJ as your Java IDE.