In Java 8, the CompletableFuture class was introduced as a powerful alternative to Future class for handling asynchronous computation. One of the key features of CompletableFuture is the ability to work with lambda expressions, allowing for concise and expressive code.

Lambda expressions, introduced in Java 8, facilitate functional programming by providing a way to pass behavior as an argument to a method. They allow you to write more compact and readable code by removing the need for anonymous classes for implementing functional interfaces.

Let’s take a look at how lambda expressions can be used in conjunction with CompletableFuture to perform asynchronous tasks.

Creating CompletableFuture with lambda expression

To create a CompletableFuture with a lambda expression, you can use the supplyAsync method. This method takes a Supplier functional interface, representing a task that produces a result of type T asynchronously.

Here’s an example of creating a CompletableFuture using a lambda expression:

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    // Perform some asynchronous computation here
    return "Result";
});

In the above example, the lambda expression () -> "Result" represents the task that will be executed asynchronously. The result of this task will be a String.

Chaining CompletableFuture with lambda expressions

One of the powerful features of CompletableFuture is the ability to chain multiple asynchronous operations together. You can use methods like thenApply, thenCompose, thenCombine, etc., to specify the next step in the asynchronous process.

Here’s an example of chaining CompletableFuture using lambda expressions:

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    // Perform some asynchronous computation here
    return "Result";
}).thenApply(result -> {
    // Transform the result asynchronously
    return result.toUpperCase();
}).thenAccept(result -> {
    // Process the transformed result asynchronously
    System.out.println("Transformed result: " + result);
});

In the above example, the thenApply method takes a Function functional interface, where you can transform the result of the previous CompletableFuture operation. The thenAccept method takes a Consumer functional interface, allowing you to process the result asynchronously.

Exception handling with lambda expressions

Lambda expressions in CompletableFuture also provide a convenient way to handle exceptions in asynchronous code.

Here’s an example of handling exceptions with lambda expressions:

CompletableFuture<String> future = CompletableFuture.supplyAsync(() -> {
    // Perform some asynchronous computation here
    throw new RuntimeException("Something went wrong");
}).exceptionally(ex -> {
    // Handle the exception asynchronously
    System.out.println("Exception: " + ex.getMessage());
    return "Default Result";
});

In the above example, the exceptionally method allows you to handle exceptions thrown by the previous stage of the CompletableFuture and provide a default result in case of an exception.

Conclusion

Lambda expressions in Java 8 CompletableFuture class provide a concise and expressive way to work with asynchronous computations. By leveraging lambda expressions, you can write more readable and maintainable code when dealing with CompletableFuture operations.

Make sure to use lambda expressions effectively in your code to take advantage of the power and flexibility they offer.

For more information on CompletableFuture and lambda expressions, you can refer to the official Java documentation:

• CompletableFuture
• Lambda Expressions

#java #completablefuture