Java has been around for two decades, and it's still one of the most widely used languages for server-side development. The skills of twenty years ago won't help youremployment prospects, though; you have to keep up on the latest technologies.

Mandatory skills include Maven and Git. Ant is old tech; complex modern projects requires Maven's dependency management. Git isn't just for open source, but for proprietary projects as well. Some employers do use other tools, but not nearly as many jobs will be open to you if you aren't comfortable with these two.

Understanding NoSQL databases is important. This is more a buzzword than a technology, since it simply means databases that don't use SQL, but you have to know about the landscape. Knowing about the Spring Data project, which includes subprojects for popular NoSQL databases, is a good start.

HTTP/2 is going to replace the less efficient HTTP/1.1, and you'll need to learn a new set of best practices to deliver pages efficiently. Understanding and being able to talk about these differences could help you to land a job. Full HTTP/2 support won't be available until Java 9, but you should be ready for it.

Knowing how to create distributed applications that don't have hard-to-find timing bugs is another vital skill. Developers are furiously debating the best approaches to distributed architecture, and you need to keep up on the current trends. Stay aware of current approaches to scalability, RESTful APIs, and load balancing.

Learn about the new Date and Time API. Everyone knows how clumsy the old Date and Calendar classes are, and when you're tracking events from all over the world, improvements such as the explicit ability to deal with local times can give you cleaner code.