An Interface that contains exactly one abstract method is known as functional interface. It can have any number of default, static methods but can contain only one abstract method. It can also declare methods of object class.
Functional Interface is also known as Single Abstract Method Interfaces or SAM Interfaces. It is a new feature in Java, which helps to achieve functional programming approach.
@FunctionalInterface annotation is added so that we can mark an interface as functional interface.
It is not mandatory to use it, but it’s best practice to use it with functional interfaces to avoid addition of extra methods accidentally.
The major benefit of java 8 functional interfaces is that we can use lambda expressions to instantiate them and avoid using bulky anonymous class implementation.
Nesta página do site você pode assistir ao vídeo on-line Functional Interface in Java8 duração hora minuto segundo em boa qualidade , que foi baixado pelo usuário Automation Testing By Experts 22 Setembro 2018, compartilhe o link com seus amigos e conhecidos, no youtube este vídeo já foi visto 264 vezes e gostou 10 espectadores. Boa visualização!