I'm adding this question because I'm new to Java and Android and I searched for hours trying to figure this out. The answer came from a combination of related answers, so I figured I'd document what I learned for anyone else who may be struggling. See answer.
For a bit of background, my experience is mostly web development in PHP and a little bit of Ruby. My only OS is Linux (Ubuntu Studio), and I'm (begrudgingly) developing my first Android app in Android Studio 2.1.2. My Java setup is the following:
>java -version > openjdk version "1.8.0_91" > OpenJDK Runtime Environment (build 1.8.0_91-8u91-b14-3ubuntu1~15.10.1-b14) > OpenJDK 64-Bit Server VM (build 25.91-b14, mixed mode)