Advanced - Functional Interfaces, Lambdas, etc.

Question 1

What are functional interfaces? List some that come with the JRE for Java 8

Answer 1

A functional interface is an interface that contains only one abstract method. They can have only one functionality to exhibit. From Java 8 onwards, lambda expressions can be used to represent the instance of a functional interface. A functional interface can have any number of default methods.

• Runnable
• ActionListener
• Comparable
• Comparator

Question 2

What are lambdas?

Answer 2

A lambda expression is a short block of code which takes in parameters and returns a value. Lambda expressions are similar to methods, but they do not need a name and they can be implemented right in the body of a method.