When you’re asking a question about a package, it’s important to be specific about the name of the package. There may be multiple packages that compile Java and they might work differently.
Fortunately, your issue is not a package problem. You need to go to
Control Panel -> System -> Advanced System Settings -> Environment Variables. In the bottom panel, locate and select
Path, click on
Edit, and then
Add a new entry, with the text
C:\Program Files\Java\jdk1.8.0_101\bin. Close the Atom application completely and reopen it and you should be able to compile things just fine. You can verify that the command works by typing
javac into the command prompt. If it works, it will give you a bunch of lines of help for how to use the command.