The Java language itself, as opposed to the classes, interfaces, and so on, is defined in the Java language specification, which can be found online. You can either view the online HTML version, or download a copy to your own system in several formats from this location:
http://java.sun.com/docs/books/jls/
This describes how Java programs are put together. It's not an easy read, it's written for compiler implementors more than it's written for programmers.
Look for "API, Language, and Virtual Machine Documentation", the link to view or download this document is in that section, titled "The Java Language Specification."
There are a few items of clarity in the document, like the section on Blocks (code blocks.)
For most programmers, especially beginners, the time to refer to this document is when you have a specific question in mind about some code you're writing that doesn't seem to want to compile. If you take a look at it occasionally, however, looking up things that you do understand and feel like you've got a handle on, it'll start making sense. Then you'll be able to make more use of it as your Java programming ability grows.