For an introduction to Java interfaces, including the difference between classes and interfaces, see my Java 101 tutorial Working with interfaces in Java. Nesting interfaces in classes Java lets ...

As I was thinking about the remaining differences between Java interfaces and abstract classes in a JDK 8 world, I decided to see what the Java Tutorial had to say on this.

In other words, a Java class that supports the SOLID open-closed principle will find use in originally un-envisioned scenarios, and be flexible enough to work with newly created classes, interfaces ...