A free app for Android, by Awwalsoft.

Java Basics Learning: Java for Absolute Beginners is an educational app that is designed to be a quick and convenient way for absolute beginners to learn the basics of Java programming. The app has been built with the user in mind. That is why we have included an easy and intuitive interface, as well as the basic elements that are necessary for the app to work. 

The interface has been designed to be as simple as possible, so that the user can get the basic idea of what the app is all about in the first few seconds of usage. After that, the user can choose to either select a topic to learn more about, or can go ahead and choose to do a full-fledged programming exercise.