This course kickstarts the whole tutoring course. It talks about softwares, code, compilers, IDE, and Hello world. It is meant to have a proper environment for the next session, and understand the basic of programming.
Here is the thing: you can't learn if you don't try. In this section, you will build a full classic morpion game. Pay attention to bold, underline or italic words as they can help you defining entities and services ... :)
Code academy - This website provides step by step tiny exercices, just to make you familiar with Java syntax, and some OO java aspects. It auto-tests your code, like an IDE and help you along the way.
Codingame - This one is a really cool one. It provides an entire "IDE" and go through some serious games to build from simple to difficult Java programs. It also has a team aspect, meaning that you can build things with your friends.
A course that go through pretty much every Java basics (conditions, for, while, fields, methods, visibility, class, object, exceptions, ...
The MIT course that takes some common mistakes, go through Java, from type to Interfaces and Inheritance and so on.