After doing a couple of mockup-exams, I realised that it is necessary to be familiar with a code that does compile, just as much as with code that does NOT compile. Following examples include both forms of code. Incorrect statements are commented out, and can be easily transformed back to code that throws compile-time errors.
The examples are not ordered in any way. They are just grouped by similarity (eg. arrays, flowcontrol, lambdas, exceptions, etc.)
One code example is not necessarily designed to explain only one thing; it can illustrate several syntactic or programming principles of Java language.
One example is not enough to explain or understand a principle: therefore, code contains seemingly redundant lines of code that nonetheless help in acquiring the pattern behind the particular case.