The Java Runtime Environment is an essential download if you want to run software written in Java. The idea is that a program written in Java will work on any computer as long as the Runtime Environment is installed, whether that is Windows, Mac or Linux.

There is an online installer that can be downloaded from the Java.com website. It scans the computer and downloads only the required files. The download from this page is the complete installer. It is the best option if the computer does not already have Java or you want to install it on more than one computer.

More information about writing software in Java, along with a Software Development Kit (SDK) can be found at http://java.sun.com/