CompletableFuture: Introduction

Introduction to CompletableFuture interface

A CompletableFuture is a class in Java that belongs to the java.util.concurrent package.

It is used for asynchronous computation. The code is executed as a non-blocking call in a separate thread, and the result is made available when it is ready.

By doing this, the main thread does not block/wait for the completion of the task, and it can execute other tasks in parallel.

The CompletableFuture class implements the CompletionStage and Future interface. The CompletionStage is a promise. It promises that the computation eventually will be done.

Before Java 8, Future interface, which was added in Java 1.5, was available for asynchronous computation. The limitation of Future interface is that it does not have any methods to combine these computations or handle errors. We will address more limitations of Future interface in the next section.

CompletableFuture has lots of different methods for composing, combining, executing asynchronous computation steps, and handling errors.