It’s a good idea to use an abstract class when you need to implement mutable state. As an example, the Java Collections Framework includes the AbstractList class, which uses the state of variables.

public abstract class Ellipse2D extends RectangularShape ... passing anonymous class-based functionality can lead to verbose syntax. Starting with Java 8, you can use lambdas for more concise ...

For this Java Function interface example, we will provide a single method named ... as is the case with object models designed with abstract classes and interfaces. Power through simplicity is exactly ...