Java Interview Questions

Anonymous Inner Class

In Java, anonymous inner classes provide a way to implement classes that may occur only once in an application.

Function Interface

With Java SE 8, an interface that follows this pattern is known as a "functional interface."

@FunctionalInterface is a new interface added in Java 8 to indicate that an interface type declaration is intended to be a functional interface as defined by the Java Language Specification.
Functional Interfaces can have only one abstract method. If you try to add one more abstract method in it, it throws compile time error.

Marker interface

Marker interface is an interface with no methods or fields declaration. In simple words, marker interface is an empty interface.