What is CompletableFuture in Java?

CompletableFuture is an enhanced version of the Future interface that supports advanced asynchronous programming in Java. It allows tasks to run independently without blocking the main thread and provides powerful features for chaining operations, combining multiple asynchronous tasks, and handling exceptions in a fluent and non-blocking way.

Key Points: • Unlike Future, CompletableFuture supports callback methods such as thenApply(), thenAccept(), and thenCompose() for task chaining. • Multiple asynchronous operations can be combined and executed efficiently without manually managing threads. • It provides built-in exception handling methods like exceptionally() and handle(), making asynchronous code more robust.

Example: In an e-commerce application, product details, pricing information, and inventory status can be fetched from different services simultaneously. CompletableFuture allows these operations to run in parallel and combines the results once all tasks are completed.

Code Example:

import java.util.concurrent.CompletableFuture;

public class CompletableFutureExample {

    public static void main(String[] args) {

        CompletableFuture<String> future =

CompletableFuture.supplyAsync(() -> "Java")

                                 .thenApply(result -> result + " CompletableFuture");

        future.thenAccept(System.out::println);

        future.join();
    }
}

Interview Tip: A concise interview answer is: CompletableFuture is an advanced implementation of Future that enables non-blocking asynchronous programming. It supports task chaining, combining multiple asynchronous operations, and exception handling, making it more powerful and flexible than the traditional Future interface.