What is the use of CompletableFuture in Java?

A CompletableFuture is an extension to Java’s Future API which was introduced in Java 8. A Future is used for asynchronous Programming. It provides two methods, isDone() and get(). The methods retrieve the result of the computation when it completes.

Where is CompletableFuture used?

20 Examples of Using Java’s CompletableFuture

1. Creating a Completed CompletableFuture.
2. Running a Simple Asynchronous Stage.
3. Applying a Function on the Previous Stage.
4. Asynchronously Applying a Function on a Previous Stage.
5. Asynchronously Applying a Function on a Previous Stage Using a Custom Executor.

What is Future object and how Future is different from CompletableFuture?

While using Future, we do not get notified when it is complete neither does it provides us a callable method which will automatically be called when the result is available but CompletableFuture provides us with a lot of callable methods which can be used as per our use case.

Which method of CompletableFuture class accepts an instance of the functional interface supplier?

The thenApply method does exactly that; it accepts a Function instance, uses it to process the result, and returns a Future that holds a value returned by a function: CompletableFuture completableFuture = CompletableFuture.

What is Future and CompletableFuture in Java?

CompletableFuture is an extension to Java’s Future API which was introduced in Java. A Future is used as a reference to the result of an asynchronous computation. It provides an isDone() method to check whether the computation is done or not, and a get() method to retrieve the result of the computation when it is done.

What is ExecutorService Java?

The Java ExecutorService is a construct that allows you to pass a task to be executed by a thread asynchronously. The executor service creates and maintains a reusable pool of threads for executing submitted tasks.

What’s the difference between future and FutureTask in Java?

1. Future is a base interface and defines the abstraction of an object which promises results to be available in the future while FutureTask is an implementation of the Future interface.

What is future and CompletableFuture in Java?

What is asynchronous in Java?

Asynchronous Callback An Asynchronous call does not block the program from the code execution. When the call returns from the event, the call returns back to the callback function. So in the context of Java, we have to Create a new thread and invoke the callback method inside that thread.

Where is asynchronous programming used?

Asynchronous is best suited when processing the following requests:

1. I/O bound requests. Examples : writing/reading to a file or database, making API calls, calling hardware like printers etc.
2. CPU bound requests (requires CPU time).

Is CompletableFuture reactive programming?

Java CompletableFuture API vs Reactive Streams The main difference is that a CompletableFuture represents one result of an asynchronous call, while Reactive Streams is a pattern for pushing N messages asynchronously through a system.

What is the difference between future and completablefuture in Java?

Future vs. CompletableFuture A CompletableFuture is an extension to Java’s Future API which was introduced in Java 8. A Future is used for asynchronous Programming. It provides two methods, isDone () and get ().

What is complea completablefuture?

A CompletableFuture is an extension to Java’s Future API which was introduced in Java 8. A Future is used for asynchronous Programming. It provides two methods, isDone () and get (). The methods retrieve the result of the computation when it completes. A Future cannot be mutually complete.

When more than one thread attempt to complete a completablefuture?

When more than one thread attempt to complete – complete exceptionally or cancel a CompletableFuture, only one of them succeeds. A CompletableFuture is an extension to Java’s Future API which was introduced in Java 8. A Future is used for asynchronous Programming.

How to get result from completablefuture using performasync in Java?

Let’s create a simple example. In the above example, we have created an instance of CompletableFuture using no-arg constructor. Hence, any client API who want to get the result from performAsync can call get () to get the result from the CompletableFuture. In the above example get () method blocks until and unless the Future completes its task.