The Java Tutorial goes on to list bullets for when an abstract class should be considered and for when an interface should be considered. Unsurprisingly, these are derived from the previously ...

Interfaces” from April 2001. A recurring request asks to see a complete example of using interfaces and abstract classes.

Functional supplier interface in Java tutorial There are only half a dozen classes you really need to master to become competent in the world of functional programming. The java.util.function package ...