Syntax wise or programming wise, it shouldn't be anything new. You've got classes, interfaces, enums. Occasionally one meats unusual constructs, such as local classes or tags, but those are the things you can learn on the fly.
What usually tends to be a lot more important is a solid grasp of the standard library, especially the collection framework (https://docs.oracle.com/javase/tutorial/collections/index.html) and the I/O package (https://docs.oracle.com/javase/7/docs/api/java/io/package-summary.html). Also, depending on what {build system, testing framework} you will be using, consider learning it's basics, so that you don't waste your time trying to get things to work, when you would want to be working.