I personally prefer making a custom script for adding environmental variables like the one mentioned by danicotra. Manually adding (and remembering) them after a reinstallation, setting up a a new computer, etc.. can be pretty annoying. Especially when your custom EnVar paths get bigger and start including more tools. ie: more than one programming language or custom CLI tools gathered over time.
You can save the following as a .bat
file and execute for automatically adding custom paths to the existing EnVars. Needs Admin privileges.
:: Set Path variable equal to existing path plus specified directory.
setx PATH "%PATH%;C:\Program Files\Java\jdk1.8.0_31\bin\;" /m
:: Add Custom path to existing envars
setx JAVA_PATH "C:\Program Files\Java\jdk1.8.0_31\bin\;" /m