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.