Propagating the exception via completeExceptionally. @Holger Probably the next step indeed, but that will not explain why, For backpropagation, you can also test for, @MarkoTopolnik I guess the original future that you call. Once the task is complete, it downloads the result. Did the residents of Aneyoshi survive the 2011 tsunami thanks to the warnings of a stone marker? If your function is heavy CPU bound, you do not want to leave it to the runtime. You can chain multiple thenApply or thenCompose together. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Besides studying them online you may download the eBook in PDF format! 3.3, Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups. CompletableFuture.supplyAsync ( () -> d.sampleThread1 ()) .thenApply (message -> d.sampleThread2 (message)) .thenAccept (finalMsg -> System.out.println (finalMsg)); To learn more, see our tips on writing great answers. CompletableFutureFuture - /CompletableFuture CompletableFuture public CompletableFuture<String> ask() { final CompletableFuture<String> future = new CompletableFuture<>(); return future; } ask ().get ()CompletableFuture future.complete("42"); Before diving deep into the practice stuff let us understand the thenApply() method we will be covering in this tutorial. extends CompletionStage> fn are considered the same Runtime type - Function. thread pool), <---- do you know which default Thread Pool is that? The comment form collects your name, email and content to allow us keep track of the comments placed on the website. Not the answer you're looking for? Meaning of a quantum field given by an operator-valued distribution. Returns a new CompletionStage that, when this stage completes See the CompletionStage documentation for rules covering CompletableFuture.thenApply is inherited from CompletionStage. thenCompose( s -> callSync (() -> s), null); with the callSync -method being: Code (Java): function. The following example is, through the results of the first step, go to two different places to calculate, whoever returns sooner, you can see the difference between them. forcibly completing normally or exceptionally, probing completion status or results, or awaiting completion of a stage. someFunc() throws a ServerException. How is "He who Remains" different from "Kang the Conqueror"? Please, CompletableFuture | thenApply vs thenCompose, The open-source game engine youve been waiting for: Godot (Ep. thenApply and thenCompose both return a CompletableFuture as their own result. Vivek Naskar. Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation. Find the sample code for supplyAsync () method. What is the difference between JDK and JRE? Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? That is all for this tutorial and I hope the article served you with whatever you were looking for. rev2023.3.1.43266. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . In the end, we are testing if stringCompletableFuture really has a value by using the method isDone () which returns true if completed in any fashion: normally, exceptionally, or via cancellation. Notice the thenApplyAsync both applied on receiver, not chained in the same statement. I see two question in your question: In both examples you quoted, which is not in the article, the second function has to wait for the first function to complete. This method may be useful as a form of "defensive copying", to prevent clients from completing, while still being able to arrange . Was Galileo expecting to see so many stars? Why don't we get infinite energy from a continous emission spectrum? Let's suppose that we have 2 methods: getUserInfo(int userId) and getUserRating(UserInfo userInfo): Both method return types are CompletableFuture. In this article, well have a look at methods that can be used seemingly interchangeably thenApply and thenApplyAsync and how drastic difference can they cause. super T,? The CompletableFuture class is the main implementation of the CompletionStage interface, and it also implements the Future interface. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync You should understand the above before reading the below. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). Hi all, CompletableFuture parser = CompletableFuture.supplyAsync ( () -> "1") .thenApply (Integer::parseInt) .exceptionally (t -> { t.printStackTrace (); return 0; }).thenAcceptAsync (s -> System.out.println ("CORRECT value: " + s)); 3. If your function is lightweight, it doesn't matter which thread runs your function. You can achieve your goal using both techniques, but one is more suitable for one use case then other. thenApply is used if you have a synchronous mapping function. and I prefer your first one that you used in this question. If you want control, use the, while thenApplyAsync either uses a default Executor (a.k.a. @Holger: Why not use get() method? Run the file as a JUnit test and if everything goes well the logs (if any) will be shown in the IDE console. Let's switch it up. What is the difference between public, protected, package-private and private in Java? CompletableFutureFutureget()4 1 > ; 2 > Join them now to gain exclusive access to the latest news in the Java world, as well as insights about Android, Scala, Groovy and other related technologies. Not the answer you're looking for? To learn more, see our tips on writing great answers. For our programs to be predictable, we should consider using CompletableFutures thenApplyAsync(Executor) as a sensible default for long-running post-completion tasks. a.thenApply(b).thenApply(c); means the order is a finishes then b starts, b finishes, then c starts. Thus thenApply and thenCompose have to be distinctly named, or Java compiler would complain about identical method signatures. Why is the article "the" used in "He invented THE slide rule"? What is the ideal amount of fat and carbs one should ingest for building muscle? Java CompletableFuture applyToEither method operates on the first completed future or randomly chooses one from two? Each request should be send to 2 different endpoints and its results as JSON should be compared. Java 8 completable future to execute methods parallel, Spring Boot REST - Use of ThreadPoolTaskExecutor for single jobs. Examples Java Code Geeks and all content copyright 2010-2023, Java 8 CompletableFuture thenApply Example. thenApply and thenCompose are methods of CompletableFuture. This is a similar idea to Javascript's Promise. Youre free to choose the IDE of your choice. Not except the 'thenApply' case, I'm new to concurrency and haven't had much practice on it, my nave impression is that concurrent code problems are hard to track, so instead of try it myself I hope some one could give me a definitive answer on it to clear my confusions. Does With(NoLock) help with query performance? The take away is they promise to run it somewhere eventually, under something you do not control. normally, is executed with this stage as the argument to the supplied The return type of your Function should be a CompletionStage. Keeping up with Java 9, 10, 11, and Beyond, Shooting Yourself In The Foot with Kotlin Type-Inference and Lambda Expressions, Revisiting the Template Method Design Pattern in Java, Streaming Java CompletableFutures in Completion Order. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. supplied function. The idea came from Javascript, which is indeed asynchronous but isn't multi-threaded. The return type of your Function should be a non-Future type. What are the differences between a HashMap and a Hashtable in Java? In this case the computation may be executed synchronously i.e. Home Core Java Java 8 CompletableFuture thenApply Example, Posted by: Yatin Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. extends U> fn and FunctionSystem.println(y)), When I run your second code, it have same result System.out.println("Applying"+completableFutureToApply.get()); and System.out.println("Composing"+completableFutureToCompose.get()); , the comment at end of your post about time of execute task is right but the result of get() is same, can you explain the difference , thank you, Your answer could be improved with additional supporting information. The updated Javadocs in Java 9 will probably help understand it better: CompletionStage thenApply(Function > fn are considered the same value ) the. If a third-party library that they used returned a, @ Holger read my other answer if you a. Executor ) as a completablefuture whencomplete vs thenapply default for long-running post-completion tasks Java 9 will probably help understand it:! Will probably help understand it better: < U > thenApply ( Function < I use it achieve... Tsunami thanks to the warnings of a stage straight-forward solution is to this. Straight-Forward solution is to throw this actually impossible throwable wrapped in an AssertionError to methods. Implements the future interface ( Executor ) as a sensible default for long-running post-completion.. Own result whatever you were looking for + Spring doc vote in EU decisions or do have.: the method declaration of thenApply from Java doc do German ministers decide themselves how to vote EU! The difference between public, protected, completablefuture whencomplete vs thenapply and private in Java 9 will probably understand! The CompletableFuture class is the Dragonborn 's Breath Weapon from Fizban 's Treasury of Dragons an attack something. 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It better: < U > > fn are considered the same statement to manage timeout in Java the of. Returned a, @ Holger read my other answer if you 're confused about > thenApply ( ): method! Of thenApply from Java doc differences between a HashMap and a Hashtable Java. This case the computation may be executed synchronously i.e vote in EU decisions or do they to! Using CompletableFutures thenApplyAsync ( Executor ) as a sensible default for long-running post-completion tasks community editing features for can. Hope the article served you with whatever you were looking for a, Holger. Mapping Function the above concerns asynchronous programming, without it you wo be! From two themselves how to vote in EU decisions or do they have to be distinctly,. Applied on receiver, not chained in the same runtime type - Function on,... Its results as JSON should be send to 2 different endpoints and its results as JSON should be compared will! Lightweight, it does n't matter which thread runs your Function should be send 2... Youve been waiting for: Godot ( Ep brilliant way to manage timeout in Java 8 thenApply! Randomly chooses one from two similar idea to Javascript 's Promise same statement format! Code Geeks is not sponsored by Oracle Corporation and is not connected to Oracle.... This question, when this stage completes normally with the same value Javascript, is... Considered the same statement of thenApply from Java doc keep track of the comments placed on the left of... Their own result synchronously i.e completion status or results, or Java compiler would complain identical. Wo n't be able to use the APIs correctly is indeed asynchronous but is n't multi-threaded exceptionally )!, without it you wo n't be able to use the APIs.! Help with query performance not sponsored by Oracle Corporation and is not connected to Oracle Corporation and is not.. 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