When default methods were introduced in Java 8, some developers thought they would be the same as abstract classes. That’s not true, however, because interfaces can’t have state. A default ...

public abstract class Ellipse2D extends RectangularShape ... Declaring a local class within an enclosing class instance method (EnclosingClass.java, version 3) class EnclosingClass { void ...

protected and private concrete methods, while interfaces have all fields as automatically public, static and final. Interfaces, however, support multiple inheritances where abstract classes don't.

The Java code below shows the details of how to use a ... Suppose we have ten such local stateful objects in class, then we need ten abstract methods for the sole purpose of enabling unit-testing. It ...