Asynchronous File Processing with CompletableFuture

Welcome to the course on Mastering Java Concurrency with Practice! In this course, we’ll explore how to apply concurrency utilities such as Semaphores, Phasers, CompletableFuture, and more to real-world problems. Each unit will introduce a problem scenario, walk through its solution using concurrency tools, and follow up with similar practice problems to reinforce your understanding.

In this unit, we focus on Asynchronous File Processing using CompletableFuture. This lesson will build on the concurrency concepts you’ve already learned, showing you how to handle multiple file operations asynchronously and keep your programs efficient and responsive.

In this unit, you’ll learn how to:

• Apply CompletableFuture to handle asynchronous tasks.
• Manage exceptions in an asynchronous environment.
• Combine multiple asynchronous operations.
• Aggregate results from concurrent file tasks efficiently.

By now, you should be comfortable with basic threading concepts, so we’ll dive deeper into how asynchronous file processing works in practice using CompletableFuture.

In a previous lesson, you learned about CompletableFuture, a versatile class in Java’s java.util.concurrent package that simplifies asynchronous programming. It allows you to handle tasks without blocking the main thread, combine multiple asynchronous computations, handle exceptions gracefully, and chain operations together.

As a quick recap:

• supplyAsync() runs a task asynchronously and returns a CompletableFuture representing the future result of that task.
• thenApply() and thenAccept() allow you to process the result of a completed task.
• exceptionally() provides a way to handle exceptions in an asynchronous pipeline.

In this lesson, we’ll use CompletableFuture to process a series of text files asynchronously. Each file will be processed on a separate thread, and once all files have been processed, we’ll aggregate the results to get a total word count. This approach will allow us to process multiple files simultaneously, improving efficiency and responsiveness, particularly when dealing with large files.

Now, let’s see how to set up the AsynchronousFileProcessing class and its methods.