In this Java 101 tutorial, I’ve explained how interfaces differ from classes, and showed you how to declare, implement, and extend interfaces in your Java programs.

When to use interfaces in Java. Interfaces are very useful for decoupling code and implementing polymorphism.We can see an example in the JDK, with the List interface: ...

There are over 40 functional interfaces listed in the java.util.functions package, which can make the prospect of functional programming in Java a somewhat daunting task. ... Learn Java lambda syntax ...