A method might accept a specific type and its subclasses, but you want to restrict usage to a select few implementations of your own design. Java's open inheritance model can feel like an open ...

The Collections class’s methods for obtaining empty collections are preferable to use of Collections ‘s similarly named fields for that same purpose because of the type safety the methods provide.

Abstract classes and interfaces in Java serve fundamentally different purposes. Learn the differences between these Java language elements and how to use them in your programs.

Even the most complicated classes in Java can be flattened down to nothing more than the set of primitive data types they represent. But primitive types aren’t objects, and that presents a problem.