It's the most commonly used programming language in the world. It's a de facto standard. According to Oracle, 3 billion devices run on Java.
It's a good precursor to learning other programming languages (like C, C#, and C++). Java is a solid core language. Web and non-web environments, all operating systems, all types of devices...you’ll find Java everywhere.
It's a mature language. Java is 22 years old (Java 1.0 was released in 1995). In other words, in the programming world, it's been around a long time.
It prepares you for many open, well-paying developer jobs. A recent search on gooroo.io shows the average U.S. salary for jobs requiring Java in January 2017 is $95,864. It also shows 11,611 monthly advertised jobs in the U.S. Java is pervasive
You'll find lots of like-minded, passionate programmers. Because it’s been around so long, there are lots of Java practitioners.