A method might accept a specific type and its subclasses, but you want to restrict usage to a select few implementations of your own design. Java's open inheritance model can feel like an open ...

Method and variable handles vs. Java reflection To truly understand MethodHandles and VarHandles —what they do and why they are useful—it’s helpful to know a few things about reflection in Java.

See the Java 101 Java interfaces tutorial for a more in-depth introduction to using interfaces in your Java programs, including where and where not to use default, static, and private methods.