Functional interface in java 8 geeksforgeeks

Zora 145 Published: 11/05/2024

Functional interface in java 8 geeksforgeeks

I'm sorry, but I can't respond in English only because of the rules mentioned earlier. However, I'd be happy to help you with functional interfaces in Java 8 and GeeksforGeeks.

In Java 8, a functional interface is an interface that has only one abstract method (also known as a single abstract method or SAM). This allows us to treat instances of such interfaces as lambda expressions or method references. Here are the key points about functional interfaces:

A functional interface must have exactly one abstract method: The interface can have multiple default methods, static methods, and constants, but it should only have one non-default abstract method. The interface can extend other interfaces: It is allowed to extend other interfaces as long as it satisfies the single abstract method rule.

Some examples of functional interfaces in Java are:

Runnable: Has a single abstract method run() Callable: Has a single abstract method call() Predicate<T>: Has a single abstract method test(T t)

Function<T, R>: Has a single abstract method apply(T t) Supplier<T>: Has a single abstract method get()

Here is an example of using a functional interface as a lambda expression:

@FunctionalInterface
interface MyPredicate {
boolean test(int x);
}
public class Main {
public static void main(String[] args) {
MyPredicate p = x -> x % 2 == 0;
System.out.println(p.test(4)); // prints: true
}
}

In this example, we define a functional interface MyPredicate with a single abstract method test(int x). We then create an instance of the interface using a lambda expression and call its test() method.

GeeksforGeeks provides a comprehensive guide to functional interfaces in Java 8, including examples and practice problems. Some of the key topics covered include:

Understanding functional interfaces Creating functional interfaces Using functional interfaces as lambda expressions or method references Converting lambda expressions to method references Handling exceptions with functional interfaces

Here is an example from GeeksforGeeks:

interface GFG {
int test(int x);
}
public class Main {
public static void main(String[] args) {
GFG f = (int n) -> { return n * 2; };
System.out.println(f.test(10)); // prints: 20
}
}

In this example, we define a functional interface GFG with a single abstract method test(int x). We then create an instance of the interface using a lambda expression and call its test() method.

I hope this helps! Let me know if you have any further questions.

What are functional interfaces in Java 8?

Functional interfaces in Java 8 are a type of interface that contains a single abstract method (SAM). A SAM is an abstract method that does not have any implementation, meaning it has to be implemented by its subclasses or classes that implement the interface.

A functional interface can be used with lambda expressions to create objects that implement the interface. This allows developers to write concise and expressive code that uses functions as first-class citizens.

Here are some key characteristics of functional interfaces:

Single Abstract Method (SAM): The most important characteristic is that it should contain a single abstract method that does not have any implementation. No default methods: A functional interface cannot have any default methods or static methods. Exactly one abstract method: It must have exactly one abstract method, which means no more and no less.

Examples of built-in functional interfaces in Java 8 include:

Runnable: This is a SAM that has an empty implementation. It's used for running a piece of code without returning any value. Callable<T>: This is a SAM that returns a value of type T. It's used for executing a piece of code that returns a value. Predicate<T>: This is a SAM that takes in one argument and returns a boolean value indicating whether the predicate is true or false. It's often used to filter data based on a certain condition. Function<T, R>: This is a SAM that takes in one argument of type T and returns a value of type R. It's often used for mapping data from one type to another.

You can create your own functional interfaces by defining a simple interface with a single abstract method. For example:

@FunctionalInterface
public interface MyFunction {
int add(int x, int y);
}

With this interface, you can use lambda expressions to create objects that implement the MyFunction interface:

MyFunction myFunction = (x, y) -> x + y;
int result = myFunction.add(2, 3); // returns 5

Functional interfaces are a powerful feature in Java 8 that allows developers to write more concise and expressive code. They can be used for a wide range of purposes, from simple tasks like running code or filtering data to complex tasks like processing streams or building reactive systems.

In conclusion, functional interfaces in Java 8 are a type of interface that contains a single abstract method (SAM). They can be used with lambda expressions to create objects that implement the interface. This allows developers to write concise and expressive code that uses functions as first-class citizens.