Hello, DaniWeb! Today I am in need of a Java Crash Course! Maybe a couple of (very short) source files with comments describing what things do? Any help is appriciated! I already know C++, how much does that help me?

Consider Java as C++ with training wheels. Multiple inheritance - no. Interfaces - yes (consider them as pure virtual classes without any method implementation or constructor/destructor methods). The best way to learn Java if you already know C++ pretty well is to study existing code.

Great! Thanks!

The Java language shouldn't cause you any problems at all (apart from some stuff around generics maybe) - it's just C++ for people with more than 16k RAM and no love of fatal addressing errors.
The Java API is the real issue here. Java comes as standard with a vast library of thousands of classes, and to read/write Java you need to know quite a lot about the most popular API classes. To get some focus you need to identify what kind of applications, then that will point you to the relevant API classes, eg desktop GUI, SQL, TCP/IP etc