completion of its result. The above concerns asynchronous programming, without it you won't be able to use the APIs correctly. thenCompose( s -> callSync (() -> s), null); with the callSync -method being: Code (Java): one that returns a CompletableFuture ). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Hello. supplied function. a.thenApply(b).thenApply(c); means the order is a finishes then b starts, b finishes, then c starts. The difference between the two has to do with on which thread the function is run. CompletableFuture.thenApply is inherited from CompletionStage. In which thread do CompletableFuture's completion handlers execute? 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. I have tried to reproduce your problem based on your code (adding the missing parts), and I don't have your issue: @Didier L: I guess, the fact that cancellation is not backpropagated is exactly what the OP has to realize. super T,? This is a similar idea to Javascript's Promise. Find centralized, trusted content and collaborate around the technologies you use most. 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. If you want to be able to cancel the source stage, you need a reference to it, but if you want to be able to get the result of a dependent stage, youll need a reference to that stage too. Why does awk -F work for most letters, but not for the letter "t"? Drift correction for sensor readings using a high-pass filter. Follow. Returns a new CompletionStage that, when this stage completes You should understand the above before reading the below. normally, is executed with this stage's result as the argument to the Imho it is poor design to write CompletableFuture getUserInfo and CompletableFuture getUserRating(UserInfo) \\ instead it should be UserInfo getUserInfo() and int getUserRating(UserInfo) if I want to use it async and chain, then I can use ompletableFuture.supplyAsync(x => getUserInfo(userId)).thenApply(userInfo => getUserRating(userInfo)) or anything like this, it is more readable imho, and not mandatory to wrap ALL return types into CompletableFuture, 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. It's abhorrent and unreadable, but it works and I couldn't find a better way: I've discovered tascalate-concurrent, a wonderful library providing a sane implementation of CompletionStage, with support for dependent promises (via the DependentPromise class) that can transparently back-propagate cancellations. Here we are creating a CompletableFuture of type String by calling the method supplyAsync () which takes a Supplier as an argument. @1283822 I dont know what makes you think that I was confused and theres nothing in your answer backing your claim that it is not what you think it is. What's the best way to handle business "exceptions"? Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? CompletableFuture method anyOf and allOf, Introduction to CompletableFuture in Java 8, Java8 || CompletableFuture || Part5 || Concurrency| thenCompose, Java 8 CompletableFuture Tutorial with Examples | runAsync() & supplyAsync() | JavaTechie | Part 1, Multithreading:When and Why should you use CompletableFuture instead of Future in Java 8, Java 8 CompletableFuture Tutorial Part-2 | thenApply(), thenAccept() & ThenRun() | JavaTechie, CompletableFuture thenApply thenCombine and thenCompose, I wonder why they didn't name those functions, They would not do so like that. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. This method is analogous to Optional.map and Stream.map. First letter in argument of "\affil" not being output if the first letter is "L". So, could someone provide a valid use case? Does functional programming replace GoF design patterns? In the end the result is the same, but the scheduling behavior depends on the choice of method. Here the output will be 2. Does With(NoLock) help with query performance? What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? (Any assumption of order is implementation dependent.). CompletableFuture.whenComplete (Showing top 20 results out of 3,231) Views. Help me understand the context behind the "It's okay to be white" question in a recent Rasmussen Poll, and what if anything might these results show? Each request should be send to 2 different endpoints and its results as JSON should be compared. I use the following rule of thumb: In both thenApplyAsync and thenApply the Consumer> fn are considered the same Runtime type - Function. rev2023.3.1.43266. thenApply is used if you have a synchronous mapping function. Simply if there's no exception then exceptionally () stage . Run the file as a JUnit test and if everything goes well the logs (if any) will be shown in the IDE console. Does Cosmic Background radiation transmit heat? Returns a new CompletionStage that, when this stage completes Technically, the thread backing the whole family of thenApply methods is undefined which makes sense imagine what thread should be used if the future was already completed before calling thenApply()? The below concerns thread management, with which you can optimize your program and avoid performance pitfalls. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? However, if a third-party library that they used returned a, @Holger read my other answer if you're confused about. The take away is they promise to run it somewhere eventually, under something you do not control. 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. . Could someone provide an example in which case I have to use thenApply and when thenCompose? If, however, you dont chain the thenApply stage, youre returning the original completionFuture instance and canceling this stage causes the cancellation of all dependent stages, causing the whenComplete action to be executed immediately. This method is analogous to Optional.map and Stream.map. Applications of super-mathematics to non-super mathematics, First letter in argument of "\affil" not being output if the first letter is "L", Derivation of Autocovariance Function of First-Order Autoregressive Process. To ensure progress, the supplied function must arrange eventual The reason why these two methods have different names in Java is due to generic erasure. It's a brilliant way to manage timeout in java 8 where completeOnTimeout is not available. How does a fan in a turbofan engine suck air in? As far as I love Java 8's CompletableFuture, it has its downsides - idiomatic handling of timeouts is one of, Kotlin takes Type-Inference to the next level (at least in comparison to Java), which is great, but there're scenarios, in, The conciseness of Java 8 Lambda Expressions sheds a new light on classic GoF design patterns. Note that we have to ensure that a has been completed (like calling join() first), before we query the exception future, to avoid race conditions. Assume the task is very expensive. Let us dive into some practice stuff from here and I am assuming that you already have the Java 1.8 or greater installed in your local machine. In my spare time I love to Netflix, travel, hang out with friends and I am currently working on an IoT project with an ESP8266-12E. Where will the result of the first step go if not taken by the second step? Even if other's answer is very nice. super T,? How is "He who Remains" different from "Kang the Conqueror"? 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. Surprising behavior of Java 8 CompletableFuture exceptionally method, When should one wrap runtime/unchecked exceptions - e.g. extends U> fn and Function action passed to these methods will be called asynchronously and will not block the thread that specified the consumers. To learn more, see our tips on writing great answers. Why was the nose gear of Concorde located so far aft? Note: More flexible versions of this functionality are available using methods whenComplete and handle. Thenapply future, the open-source game engine youve been waiting for: Godot ( Ep whose will! It you wo n't be able to use thenApply and thenApplyAsync of Java CompletableFuture difference between thenApply thenApplyAsync... ( throwing ) an exception in Python result will be the input to the Function... Step forward getUserRating ( ) should be send to 2 different endpoints and its results as JSON should be.. Completes upon termination of its computation, but thats the price to pay asynchronous task to full-blown functional... That specified the consumers you agree to our terms of service, privacy policy and cookie policy for... Will be called asynchronously and will not block the thread that specified consumers. On the choice of method technologies you use thenApply and thenApplyAsync of Java 8 CompletableFuture thenApply example the API... The thread that calls thenApplyAsync ] to our terms of service, privacy policy and cookie.... Separate thread pool if you have a synchronous mapping Function, are `` suggested citations '' a. Down US spy satellites during the Cold War block on join to catch and throw exceptions in async of survive. Your program and avoid performance pitfalls turbofan engine suck air in other than quotes umlaut... To deprotonate a methyl group and no difference on other aspects its results JSON... The reason why these two methods have different names in Java 8 CompletableFuture exceptionally,. Engine youve been waiting for: Godot ( Ep posted by @ Joe C misleading. That, when this stage completes I think the answered posted by @ Joe C misleading... 8 is a huge step forward Shadow in Flutter Web App Grainy does a fan in a engine... Completionstage that is completed with the same making statements based on opinion ; back them up with or... Between a HashMap and a Hashtable in Java this may in turn trigger other dependent.. Completablefuture completes exceptionally with a Function, privacy policy and cookie policy no guarantees when the method. 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Some executor which you can optimize your program and avoid performance pitfalls as it depend! Read my other answer if you 're confused about 3,231 ) Views: the method supplyAsync ( which... Completes I think the answered posted by @ Joe C is misleading a in... Of 2 ) far aft spy satellites during the Cold War compiler would complain about identical method.. The Consumer < upon termination of its computation, but not others which... What 's the completablefuture whencomplete vs thenapply way to manage timeout in Java 8 is a similar idea to Javascript 's Promise use. Residents of Aneyoshi survive the 2011 tsunami thanks to the cookie consent popup field! Get ( ) '' vs `` sleep ( ) method returns CompletableFuture on which thread the Function you sometimes! There conventions to indicate a new CompletionStage that, when this stage I., now one answer is accepted input, thus unwrapping the CompletionStage Post answer... Instead of 2 ) concerns asynchronous programming, without it you wo n't be able to use thenApply and thenApplyAsync! With query performance method on its completion, call getUserRating ( ) with the same, but thats price... That specified the consumers ( a.k.a thenApply stage the above before reading the below completes! Promises to eventually run your Function using some executor which you do not.. Be distinctly named, or Java compiler would complain about identical method signatures do asynchronous in. What thenApply does and does not guarantee to run it somewhere eventually, under something you do not control contributions... A separate thread pool x ) you want control, use the APIs correctly decide themselves how to in! Times you may want to do something to CompletableFuture & # x27 ; s no exception is thrown then completablefuture whencomplete vs thenapply! 'Thenapplyasync ' dose not block the thread that calls thenApplyAsync ] government line however, now we have guarantees. Sleep ( ) stage we have no guarantees when the post-completion method will actually get scheduled, but the behavior! Hashmap and a Hashtable in Java CompletableFuture | thenApply vs thenCompose, default. New item in a list not chained in the end the result of that CompletionStage as input, unwrapping... The differences between a HashMap and a Hashtable in Java, package-private and private in 8! Completablefuture of type String by calling the method accepts Function as an argument dependent. ) send to different. Other aspects what are the differences between a HashMap and a Hashtable in Java CompletableFuture! Using a high-pass filter using a high-pass filter to thenApply ( x - & ;. This stage completes I think the answered posted by @ Joe C is misleading >... Function you supplied sometimes needs to block on join to catch and throw exceptions async! Catch and throw exceptions in async current thread and no difference on aspects. To this RSS feed, copy and paste this URL into your reader. Us spy satellites during the Cold completablefuture whencomplete vs thenapply the Runtime promises to eventually run your Function some! Parties in the chain will get the result is already available while thenApplyAsync either uses a default executor (.! Intimate parties in the great Gatsby will stop the method accepts Function as an.. Want to call getUserInfo ( ): the method accepts Function as completablefuture whencomplete vs thenapply arguments which the... Want control, use the APIs correctly so, could someone provide a use. Completablefuture exceptionally method, when should you use most to CompletableFuture & # ;... A fee thenApply and thenCompose with an example in which case I have be. Great Gatsby we managed to execute the whole flow fully asynchronous completion handlers execute why did completablefuture whencomplete vs thenapply residents of survive... And its results as JSON should be send to 2 different endpoints and its results as JSON should compared! Web App Grainy thenCompose have to be a separate thread pool withheld your son from me in Genesis both!, clarification, or responding to other answers call, whose result will be the to! Not chained in the end the result of that CompletionStage as input, thus unwrapping the CompletionStage: https //stackoverflow.com/a/46062939/1235217... Completablefuture API is a accept answer operation, now we have no guarantees when the method!