Windows

  1. Download the latest stable release of the Java Runtime Environment (JRE)

Note: If you are unsure about the version please follow this guide from Microsoft
http://windows.microsoft.com/en-US/windows7/find-out-32-or-64-bit

Ubuntu

You can install the OpenJDK on it's own as a package

sudo apt-get install openjdk-6-jdk

or automatically as a dependency of Tomcat

sudo apt-get install tomcat6

Other Operating Systems

  1. Download the latest stable release of the Java Runtime Environment (JRE)
  2. Run the installer (or unzip the contents, whichever is needed)
  3. Accept the license agreement