How to Chain CompletableFuture Results in Java for Asynchronous Programming?

How can I effectively chain CompletableFuture results in Java to handle multiple asynchronous operations?

import java.util.concurrent.CompletableFuture;

public class CompletableFutureExample {
    public static void main(String[] args) {
        CompletableFuture<Integer> futureResult = CompletableFuture
            .supplyAsync(() -> { 
                // Simulate a long-running task
                return 5;
            })
            .thenApply(result -> {
                // Process the result
                return result * 2;
            })
            .thenApply(result -> {
                // Further process the result
                return result + 3;
            });

        // Block and get the final result
        System.out.println(futureResult.join()); // Outputs 13
    }
}

Chaining CompletableFuture results allows you to compose multiple asynchronous tasks in a sequential manner. This not only simplifies your code but also enhances readability when handling complex asynchronous workflows in Java.

CompletableFuture<Integer> processedFuture = CompletableFuture
    .supplyAsync(() -> 10)
    .thenApply(result -> result + 5)
    .thenApply(result -> result * 2);

System.out.println(processedFuture.join()); // Outputs 30

Causes

• Need for handling multiple asynchronous tasks efficiently.
• Sequential processing of results from a series of non-blocking operations.

Solutions

• Use `thenApply`, `thenCompose`, and `thenAccept` methods to chain CompletableFuture results.
• Ensure each chained step returns a CompletableFuture to maintain the asynchronous flow.

Mistake: Not handling exceptions in CompletableFutures leads to ignored failures.

Solution: Use `handle`, `exceptionally`, or `whenComplete` to manage exceptions properly.

Mistake: Blocking the main thread while waiting for CompletableFuture results leads to performance issues.

Solution: Use non-blocking calls like `join()` or use callbacks to handle results asynchronously.