Asking for help, clarification, or responding to other answers. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). Let's switch it up. rev2023.3.1.43266. Making statements based on opinion; back them up with references or personal experience. whenCompletewhenCompleteAsync 2.1whenComplete whenComplete ()BiConsumerBiConsumeraccept (t,u)future @Test void test() throws ExecutionException, InterruptedException { System.out.println("test ()"); What tool to use for the online analogue of "writing lecture notes on a blackboard"? Does java completableFuture has method returning CompletionStage to handle exception? CompletableFuture.supplyAsync supplyAsync accepts a Supplier as an argument and complete its job asynchronously. extends U> fn), The method is used to perform some extra task on the result of another task. Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on target collision resistance? ; The fact that the CompletableFuture is also an implementation of this Future object, is making CompletableFuture and Future compatible Java objects.CompletionStage adds methods to chain tasks. How to delete all UUID from fstab but not the UUID of boot filesystem. @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. Subscribe to our newsletter and download the Java 8 Features. Applications of super-mathematics to non-super mathematics. supplyAsync(() -> "Hello, World!", Executors. normally, is executed with this stage's result as the argument to the where would it get scheduled? Then Joe C's answer is not misleading. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? The above concerns asynchronous programming, without it you won't be able to use the APIs correctly. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. Not the answer you're looking for? thenApply() is better for transform result of Completable future. thenCompose is used if you have an asynchronous mapping function (i.e. Interesting question! Nice answer, it's good to get an explanation about all the difference version of, It is a chain, every call in the chain depends on the previous part having completed. I'm not a regular programmer, I've also got communication skills ;) I like to create single page applications(SPAs) with Javascript and PHP/Java/NodeJS that make use of the latest technologies. When and how was it discovered that Jupiter and Saturn are made out of gas? Your code suggests that you are using the result of the asynchronous operation later in the same method, so youll have to deal with CompletionException anyway, so one way to deal with it, is. How to draw a truncated hexagonal tiling? Find the method declaration of thenApply from Java doc. It turns out that the one-parameter version of thenApplyAsync surprisingly executes the callback on a different thread pool! This means both function can start once receiver completes, in an unspecified order. CompletableFuture . Why does awk -F work for most letters, but not for the letter "t"? The CompletableFuture API is a high-level API for asynchronous programming in Java. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? To ensure progress, the supplied function must arrange eventual super T,? Below are several ways for example handling Parsing Error to Integer: 1. But you can't optimize your program without writing it correctly. Which part of throwing an Exception is expensive? You should understand the above before reading the below. See the CompletionStage documentation for rules covering The result of supplier is run by a task from ForkJoinPool.commonPool () as default. thenCompose() is better for chaining CompletableFuture. thenApply/thenApplyAsync, and their counterparts thenCompose/thenComposeAsync, handle/handleAsync, thenAccept/thenAcceptAsync, are all asynchronous! 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. CompletableFuture implements the Future interface, so you can also get the response object by calling the get () method. Can patents be featured/explained in a youtube video i.e. Refresh the page, check Medium 's site. Can a VGA monitor be connected to parallel port? You use. Is there a colloquial word/expression for a push that helps you to start to do something? The straight-forward solution is to throw this actually impossible throwable wrapped in an AssertionError. First letter in argument of "\affil" not being output if the first letter is "L". Returns a new CompletionStage with the same result or exception as this stage, that executes the given action when this stage completes. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? value. Returns a new CompletionStage that is completed with the same If your function is lightweight, it doesn't matter which thread runs your function. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It turns out that its enough to just replace thenApply with thenApplyAsync and the example still compiles, how convenient! From tiny, thin abstraction over asynchronous task to full-blown, functional, feature rich utility. Let's suppose that we have 2 methods: getUserInfo(int userId) and getUserRating(UserInfo userInfo): Both method return types are CompletableFuture. If this CompletableFuture completes exceptionally, then the returned CompletableFuture completes exceptionally with a CompletionException with this exception as cause. The CompletableFuture class is the main implementation of the CompletionStage interface, and it also implements the Future interface. The documentation of whenComplete says: Returns a new CompletionStage with the same result or exception as this stage, that executes the given action when this stage completes. The usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. Could very old employee stock options still be accessible and viable? Does Cosmic Background radiation transmit heat? If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. rev2023.3.1.43266. Best Java code snippets using java.util.concurrent. And if you are still confused about what makes the real difference in code when I use thenApply vs thenCompose and what a nested future looks like then please look at the full working example. Each operator on CompletableFuture generally has 3 versions. This is a similar idea to Javascript's Promise. In this case the computation may be executed synchronously i.e. Why is the article "the" used in "He invented THE slide rule"? Is Java "pass-by-reference" or "pass-by-value"? Using composing you first create receipe how futures are passed one to other and then execute, Using apply you execute logic after each apply invocation. CompletableFuture | thenApply vs thenCompose, CompletableFuture class: join() vs get(), Timeout with CompletableFuture and CountDownLatch, CompletableFuture does not complete on timeout, CompletableFuture inside another CompletableFuture doesn't join with timeout, Do I need a transit visa for UK for self-transfer in Manchester and Gatwick Airport. Making statements based on opinion; back them up with references or personal experience. 542), We've added a "Necessary cookies only" option to the cookie consent popup. thenApply and thenCompose are methods of CompletableFuture. Thanks for contributing an answer to Stack Overflow! CompletableFuture.whenComplete (Showing top 20 results out of 3,231) Refresh the page, check Medium 's site status, or. Critical issues have been reported with the following SDK versions: com.google.android.gms:play-services-safetynet:17.0.0, Flutter Dart - get localized country name from country code, navigatorState is null when using pushNamed Navigation onGenerateRoutes of GetMaterialPage, Android Sdk manager not found- Flutter doctor error, Flutter Laravel Push Notification without using any third party like(firebase,onesignal..etc), How to change the color of ElevatedButton when entering text in TextField, CompletableFuture | thenApply vs thenCompose, Using composing you first create receipe how futures are passed one to other and then execute, Using apply you execute logic after each apply invocation. As titled: Difference between thenApply and thenApplyAsync of Java CompletableFuture? I added some formatting to your text, I hope that is okay. thenCompose() should be provided to explain the concept (4 futures instead of 2). Hello. What would happen if an airplane climbed beyond its preset cruise altitude that the pilot set in the pressurization system? If your function is heavy CPU bound, you do not want to leave it to the runtime. extends CompletionStage> fn are considered the same Runtime type - Function. Thus thenApply and thenCompose have to be distinctly named, or Java compiler would complain about identical method signatures. Asking for help, clarification, or responding to other answers. Can I pass an array as arguments to a method with variable arguments in Java? extends CompletionStage> fn are considered the same Runtime type - Function. doSomethingThatMightThrowAnException returns a CompletableFuture, which might completeExceptionally. Are you sure your explanation is correct? CompletableFuture#whenComplete not called if thenApply is used, The open-source game engine youve been waiting for: Godot (Ep. Was Galileo expecting to see so many stars? rev2023.3.1.43266. To ensure progress, the supplied function must arrange eventual We can also pass . Find centralized, trusted content and collaborate around the technologies you use most. Other problem that can visualize difference between those two. thenApplyAsync Will use the a thread from the Executor pool. future.get() Will block the main thread . 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, @user1694306 Whether it is poor design or not depends on whether the user rating is contained in the, I wonder why they didn't name those functions, While i understand the example given, i think thenApply((y)->System.println(y)); doesnt work. The thenApply returns a new CompletionStage that, when this stage completes normally, is executed with this stage's result as the argument to the supplied function. Let's suppose that we have 2 methods: getUserInfo(int userId) and getUserRating(UserInfo userInfo): Both method return types are CompletableFuture. Other times you may want to do asynchronous processing in this Function. value as the CompletionStage returned by the given function. runAsync supplyAsync . Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This is a very nice guide to start with CompletableFuture -, They would not do so like that. CompletableFuture<String> cf2 = cf1.thenApply(s -> s + " from the Future!"); There are three "then-apply" methods. Can patents be featured/explained in a youtube video i.e. Why was the nose gear of Concorde located so far aft? @JimGarrison. The return type of your Function should be a CompletionStage. Once when a synchronous mapping is passed to it and once when an asynchronous mapping is passed to it. You can achieve your goal using both techniques, but one is more suitable for one use case then other. mainly than catch part (CompletionException ex) ? How to convert the code to use CompletableFuture? thenApply() returned the nested futures as they were, but thenCompose() flattened the nested CompletableFutures so that it is easier to chain more method calls to it. You're mis-quoting the article's examples, and so you're applying the article's conclusion incorrectly. Does With(NoLock) help with query performance? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This method is analogous to Optional.flatMap and When calling thenApply (without async), then you have no such guarantee. non-async: only if the task is very small and non-blocking, because in this case we don't care which of the possible threads executes it, async (often with an explicit executor as parameter): for all other tasks. Here is a complete working example, I just replace the doReq by sleep because I don't have your web service: Thanks for contributing an answer to Stack Overflow! The take away is they promise to run it somewhere eventually, under something you do not control. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync, 4. Let me try to explain the difference between thenApply and thenCompose with an example. How to convert Character to String and a String to Character Array in Java, java.io.FileNotFoundException How to solve File Not Found Exception, java.lang.arrayindexoutofboundsexception How to handle Array Index Out Of Bounds Exception, java.lang.NoClassDefFoundError How to solve No Class Def Found Error, The method is represented by the syntax CompletionStage thenApply(Function action passed to these methods will be called asynchronously and will not block the thread that specified the consumers. In this case you should use thenApply. How is "He who Remains" different from "Kang the Conqueror"? To learn more, see our tips on writing great answers. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. In the end the result is the same, but the scheduling behavior depends on the choice of method. The reason why these two methods have different names in Java is due to generic erasure. CSDNweixin_39460819CC 4.0 BY-SA one that returns a CompletableFuture). All of them take a function as a parameter, which takes the result of the upstream element of the chain, and produces a new object from it. Use them when you intend to do something to CompletableFuture's result with a Function. Find centralized, trusted content and collaborate around the technologies you use most. Making statements based on opinion; back them up with references or personal experience. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Interested in a consultancy or an on-site training? CompletionException. Is it ethical to cite a paper without fully understanding the math/methods, if the math is not relevant to why I am citing it? Create a test class in the com.java8 package and add the following code to it. Java 8 completable future to execute methods parallel, Spring Boot REST - Use of ThreadPoolTaskExecutor for single jobs. I can't get my head around the difference between thenApply and thenCompose. someFunc() throws a ServerException. @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. Since I have tons of requests todo and i dont know how much time could each request take i want to limit the amount of time to wait for the result such as 3 seconds or so. Whenever you call a.then___(b -> ), input b is the result of a and has to wait for a to complete, regardless of whether you use the methods named Async or not. Not the answer you're looking for? CompletionStage. CompletionStage returned by this method is completed with the same CompletionStage. The next Function in the chain will get the result of that CompletionStage as input, thus unwrapping the CompletionStage. @ayushgp i don't see this happening with default streams, since they do not allow checked exceptions may be you would be ok with wrapping that one and than unwrapping? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, This is my new understanding: 1. it is correct to pass the stage before applying. I think the answered posted by @Joe C is misleading. whenComplete ( new BiConsumer () { @Override public void accept . Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop, jQuery Ajax error handling, show custom exception messages. CompletableFutures thenApply/thenApplyAsync areunfortunate cases of bad naming strategy and accidental interoperability. value. Home Core Java Java 8 CompletableFuture thenApply Example, Posted by: Yatin In that case you should use thenCompose. Returns a new CompletionStage that, when this stage completes normally, is executed using this stages default asynchronous execution facility, with this stages result as the argument to the supplied function. This site uses Akismet to reduce spam. Here's where we can use thenCompose to be able to "compose"(nest) multiple asynchronous tasks in each other without getting futures nested in the result. Unlike procedural programming, asynchronous programming is about writing a non-blocking code by running all the tasks on separate threads instead of the main application thread and keep notifying the main thread about the progress, completion status, or if the task fails. What is behind Duke's ear when he looks back at Paul right before applying seal to accept emperor's request to rule? Policy and cookie policy ( ) and pollRemoteServer ( jobId ) both thenApply and thenApplyAsync of Java CompletableFuture ``! Thenapply with thenApplyAsync and the example still compiles, how convenient iterating through a Collection, ConcurrentModificationException! That specified the consumers are several ways for example handling Parsing Error to Integer: 1 eventual can... Where thenApply does not its preset cruise altitude that the 2nd argument of `` \affil not! A synchronous mapping is passed to it what is the article `` the '' used in `` invented! Thencompose is used if you want to do something to CompletableFuture & # x27 ; s site want do... They used returned a, @ Holger read my other Answer if you to. It you wo n't be able to use the APIs correctly that Jupiter and Saturn made. Applying seal to accept emperor 's request to completablefuture whencomplete vs thenapply 's request to rule this will the. The Executor pool use thenCompose target collision resistance whereas RSA-PSS only relies on target collision resistance letter argument. And all content copyright 2010-2023, Java 8 CompletableFuture thenApply example, posted @. Text, i hope that is okay enough to just replace thenApply with thenApplyAsync the. To full-blown, functional, feature rich utility of `` \affil '' not being output if the first future. In Geo-Nodes was it discovered that Jupiter and Saturn are made out of gas asynchronous... For example handling Parsing Error to Integer: 1 was it discovered that and... As input, thus unwrapping the CompletionStage interface, so you 're confused about leave it the... Have i unleashed same CompletionStage the UUID of boot filesystem a consistent wave pattern a... These methods will be called asynchronously and will not block the thread completing the future interface youve been for... Similar idea to Javascript 's Promise this is a similar idea to Javascript 's Promise our of... A separate thread pool the technologies you use thenApply and thenApplyAsync of Java CompletableFuture the. Quantum field given by an operator-valued distribution common ForkJoinPool, argh eventually, something. Asynchronous Weapon damage assessment, or Java compiler would complain about identical method signatures given when! Array as arguments to a method with variable arguments in Java is a idea. May in turn trigger other dependent stages page, check Medium & # ;... Other Answer if you want to block the thread completing the future or not request should be a CompletionStage asynchronous! One that returns a new CompletionStage that, when this stage as it is easy to use the thread! May want to leave it to the where would it get scheduled intend to do processing. Passed to it thin abstraction over asynchronous task completablefuture whencomplete vs thenapply full-blown, functional, feature rich utility 8 Completable future about. > action passed to it and once when an asynchronous mapping Function ( ( method... Be executed synchronously i.e asynchronous task to full-blown, functional, feature rich utility return of! Class is the main implementation of the CompletionStage Corporation in the chain will get the response object by the! Behavior is equivalent to thenApply ( without async ), then the returned CompletableFuture completes exceptionally with a Function its. It discovered that Jupiter and Saturn are made out of gas this may in turn trigger dependent..., thus unwrapping the CompletionStage documentation for rules covering the result of the Lord say: you not. Accept emperor 's request to rule them up with references or personal experience perform some extra task the. To use and very clearly a test class in the chain will get the result of another task share... To start to do something to CompletableFuture 's result with a CompletionException with this as. The relationship of jobId = schedule ( something ) and thenCompose have to be distinctly named, Java! Different from `` Kang the Conqueror '' so far aft above before reading the below the CompletableFuture... Rule '' word/expression for a push that helps you to start to do?! Eventual super T > action passed to it would happen if an airplane climbed beyond its preset cruise that. Connect and share knowledge within a single location that is structured and easy to search > fn are considered same... The CompletableFuture API is a similar idea to Javascript 's Promise they Promise to run it somewhere eventually under. Techniques, but this may in turn trigger other dependent stages: difference between thenApply and thenCompose with an.! The cookie consent popup the supplied Function must arrange eventual super T > action passed to it before the! Use case then other 2 ) @ Joe c is misleading of method also.. ; x ) is completed with the same CompletionStage pollRemoteServer ( jobId ) - using this will the! Me try to explain the concept ( 4 futures instead of 2 ) methyl group Breath Weapon from 's! Consistent wave pattern along a spiral curve in Geo-Nodes example still compiles, how convenient surprisingly... Runtime type - Function BiConsumer & lt ; T, throwable because it is to... Game to stop plagiarism or at least enforce proper attribution a sensible default for long-running post-completion tasks those. `` \affil '' not being output if the completablefuture whencomplete vs thenapply completed future or randomly chooses one two! Scheduling behavior depends on the result of another task you use most ; x.... ; back them up with references or personal experience - similar to handle exception method declaration of thenApply Java... Task from ForkJoinPool.commonPool ( ) should be a CompletionStage when an asynchronous mapping Function ( i.e Function can once... The relationship of jobId = schedule ( something ) and pollRemoteServer ( jobId.. Completing the future interface what factors changed the Ukrainians ' belief in the end the of! On a different thread pool why these two methods have different names in Java colloquial word/expression for push. Would complain about identical method signatures thenApplyAsync will use the a thread from Executor! Paul right before applying seal to accept emperor 's request to rule several ways example. Pressurization system of ThreadPoolTaskExecutor for single jobs Promise to run it somewhere eventually, under something you do not.. 'S result as the argument to the cookie consent popup paste this URL into your RSS reader next!, posted by @ Joe c is misleading a similar idea to Javascript Promise! Of thenCompose extends the CompletionStage easy to use and very clearly case the computation may be executed i.e. Invasion between Dec 2021 and Feb 2022 i apply a consistent wave pattern along a spiral curve in.... We can also get the result of that CompletionStage as input, thus unwrapping the CompletionStage thenApply. Log, the default Executor is promised to be a CompletionStage Ukrainians ' belief in the chain get! And collaborate around the technologies you use most ) - & gt ; x ) accept emperor request. But less verbose, 3 bound, you do not want to leave it to last... Same Runtime type - Function jQuery Ajax Error handling, show custom exception messages arguments to a method variable. A colloquial word/expression for a push that helps you to start to do processing... Second step has to wait for the letter `` T '' CompletableFuture methods are supplyAsync. Achieve your goal using both techniques, but one is more suitable for one use then! A stage completes result of that CompletionStage as input, thus unwrapping the CompletionStage request rule! Will stop the method on its tracks and not execute the next Function the. With ( NoLock ) help with query performance your son from me in Genesis say: you have withheld... Concerns asynchronous programming in Java is due to generic erasure asynchronous mapping is passed to these methods be., you do not want to do something to CompletableFuture 's result as the CompletionStage interface, so you achieve! Treasury of Dragons an attack thenApply vs thenCompose, the method is completed with the,... Synchronous mapping Function ( i.e handling, show custom exception messages long-running post-completion tasks called... '' or `` pass-by-value '' readings using a high-pass filter United States and other countries to handle?... Progress, the open-source game completablefuture whencomplete vs thenapply youve been waiting for: Godot (.! Was it discovered that Jupiter and Saturn are made out of gas ( )... 'S default asynchronous Weapon damage assessment, or responding to other answers the sample for... I think the answered posted by: Yatin in that case you should thenCompose. Areunfortunate cases of bad naming strategy and accidental interoperability it somewhere eventually, under something you not... United States and other countries to wait for the result of another.! And Gatwick Airport as this stage as it is easy to use and very clearly Conqueror '' completablefuture whencomplete vs thenapply know. Logo 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA, is executed with exception. Corporation in the United States and other countries predictable, We should consider using CompletableFutures thenApplyAsync ( Executor ) default. Perform some extra task on the choice of method one is more suitable for one use then. Pollremoteserver ( jobId ) assessment, or what hell have i unleashed page... Full-Scale invasion between Dec 2021 and Feb 2022 or at least enforce attribution. Order is concerned functional, feature rich utility my video game to stop plagiarism or at least enforce attribution... When removing objects in a youtube video i.e ) ; a.thenApplyAsync ( c ) works! Thread pool completed future or randomly chooses one from two by calling the get ( should! The where would it get scheduled with references or personal experience to 2 different endpoints and its as! Structured and easy to search use them when you intend to do processing... Concurrentmodificationexception when removing objects in a youtube video i.e then you have an asynchronous mapping is passed to these will... To 2 different endpoints and its results as JSON should be provided to explain the concept 4.