Java's Custom callback interface

Essentially: Passing different implementations of the interface instances, executing different programs, that is, extensibility.

In a method, you can implement an interface in an object, instantiate the interface, and then complete different returns for different objects.

In the original class, the methods in the interface are called, and different programs are implemented according to the different interface instances.

For example:

An interface designed by yourself:

In short, interfaces make it easy to extend some classes.

Java's Custom callback interface