To lay the groundwork necessary for a clear discussion, I review Java class and interface ... hierarchy. An abstract class does not need any abstract methods; however, any class with an abstract ...

The Java 2 SDK organizes its vast collection of classes and interfaces into a tree-like hierarchy of packages ... for a subclass method to // call a superclass's protected method return super.returnz ...

The release of Java SE 15 ... page for a sealed class.) A hierarchy like Shape gives its clients a choice: they can deal with shapes entirely through their abstract interface, but they also ...