Java CompletableFuture allOf

Java CompletableFuture allOf

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allOf() is a method provided by the CompletableFuture class in Java, which allows you to combine multiple completable futures into one that completes when all of them have completed.

Here's an example:

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.TimeUnit;
public class CompletableFutureAllOfExample {
public static void main(String[] args) throws InterruptedException {
// Create three completable futures
CompletableFuture future1 = CompletableFuture.completedFuture("Future 1").thenApply(str -> str.toUpperCase());
CompletableFuture future2 = CompletableFuture.completedFuture("Future 2").thenApply(str -> str.toLowerCase());
CompletableFuture future3 = CompletableFuture.runAsync(() -> {
try {
TimeUnit.SECONDS.sleep(2);
return 42;
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
});
// Use allOf() to combine the futures
CompletableFuture combinedFuture = CompletableFuture.allOf(future1, future2, future3);
// Wait for the combined future to complete
combinedFuture.get();
}
}

In this example, we create three completable futures: future1, future2, and future3. The first two are simple futures that return strings in uppercase and lowercase respectively. The third one simulates some long-running operation by sleeping for 2 seconds.

We then use the allOf() method to combine these futures into a single future, combinedFuture. This future completes when all three of the original futures have completed.

Finally, we wait for the combined future to complete using the get() method. When this happens, we know that all three of our original futures have completed.

The benefits of allOf() are:

In summary, allOf() is a powerful method in Java that allows you to combine multiple completable futures into one, making it easier to write concurrent and asynchronous code.

CompletableFuture Java 21

CompletableFuture in Java 21

In Java 8 and later versions, the CompletableFuture class was introduced as part of the Java API to support asynchronous programming using lambda expressions and method references. It provides a powerful way to handle asynchronous computations by allowing you to compose together multiple tasks that can run concurrently or sequentially.

Key Features

Example Usage

Here's a simple example of how you might use CompletableFuture in a Java application:

import java.util.concurrent.*;
public class CompletableFutureExample {
public static void main(String[] args) throws InterruptedException, ExecutionException {
// Create a CompletableFuture that runs after 2 seconds
CompletableFuture future = CompletableFuture.runAfterDelay(() -> {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
return 42;
});
// Get the result of the future when it's complete
FutureResult result = future.whenComplete((r, ex) -> {
if (ex == null) {
System.out.println("The answer is: " + r.get());
} else {
System.out.println("An error occurred: " + ex.getMessage());
}
});
// Run the main thread for a few seconds to simulate some other work
Thread.sleep(3000);
}
}

Best Practices

When working with CompletableFuture, it's essential to follow best practices to avoid common pitfalls:

Conclusion

CompletableFuture provides a powerful way to handle asynchronous computations in Java, allowing you to create complex workflows that can run concurrently or sequentially. By following best practices and understanding its key features and usage, you can effectively use CompletableFuture to improve the performance of your applications.