Java 8 introduced a new feature called Functional Interfaces, which are also known as Single Abstract Method (SAM) interfaces. Functional interfaces are interfaces that have only one abstract method, which is used as a signature for a lambda expression. They are important because they allow us to use lambda expressions in our code, which provide a concise and readable way of implementing functionality.
In this article, we will discuss what Functional Interfaces are, why they are important, and how they work.
What are Functional Interfaces?
A Functional Interface is an interface that contains only one abstract method. It can contain any number of default and static methods, but it must have only one abstract method. An interface that has more than one abstract method is not a Functional Interface and cannot be used with lambda expressions.
Functional Interfaces are annotated with the @FunctionalInterface annotation, which is a marker annotation used to indicate that an interface is intended to be a Functional Interface.
Why are Functional Interfaces important?
Functional Interfaces are important because they allow us to use lambda expressions in our code. Lambda expressions provide a concise and readable way of implementing functionality, and they are very useful for writing functional-style code.
Functional-style code is code that is based on the principles of functional programming. Functional programming is a programming paradigm that emphasizes the use of functions to solve problems. It is a declarative style of programming, which means that it focuses on what needs to be done rather than how it needs to be done.
Functional Interfaces allow us to write code in a functional style by providing a single abstract method that represents the functionality we want to implement. We can then use lambda expressions to provide an implementation for that method.
How do Functional Interfaces work?
Functional Interfaces work by providing a single abstract method that represents the functionality we want to implement. We can then use lambda expressions to provide an implementation for that method.
For example, let’s say we have a Functional Interface called MyFunctionalInterface:
@FunctionalInterface
public interface MyFunctionalInterface {
public void doSomething();
}
This interface has only one abstract method called doSomething(). We can use a lambda expression to provide an implementation for this method:
MyFunctionalInterface myFunctionalInterface = () -> System.out.println("Doing something…");
myFunctionalInterface.doSomething();
In this example, we have created a lambda expression that implements the doSomething() method of the MyFunctionalInterface interface. We have then assigned this lambda expression to a variable of type MyFunctionalInterface.
We can then call the doSomething() method on this variable, which will execute the lambda expression and print “Doing something…” to the console.
Conclusion
Functional Interfaces are an important feature in Java 8 that allow us to write functional-style code using lambda expressions. They provide a concise and readable way of implementing functionality, and they are very useful for writing functional-style code.
By understanding how Functional Interfaces work, we can use them to write better and more expressive code that is easier to read and maintain.
