0.5. Oracle OpenJDK
We learn about the OpenJDK project and how to pick an appropriate version. Most likely, when you get a job programming Java, your employer will determine which version you will use, and it will typically not be the most recent version. Java releases new "feature releases" every 6 months and a "long-term support" version every 3 years (6 versions). The best for someone learning Java is to learn the newest versions, but to also have some understanding of what is new. It's not easy. When I started programming Java, we could learn everything there was to know in one week. Now it can take months to master the language fully. However, if you are a keen learner, this also makes it fun, because you can continually improve yourself and become a more valuable programmer.
Java programmers are in short supply. Even though there are millions of Java programmers in the world, like in everything there are some that are truly brilliant wizards of Java, a whole chunk that are mediocre at best, and an even larger group of programmers that could not code their way out of a paper bag. A good Java programmer can command an excellent salary, with signing bonuses, great perks, etc. So far I have not found one country where the supply of good Java programmers was higher than the demand.