completablefuture whencomplete vs thenapply

How can I create an executable/runnable JAR with dependencies using Maven? Flutter change focus color and icon color but not works. In which thread do CompletableFuture's completion handlers execute? To learn more, see our tips on writing great answers. doSomethingThatMightThrowAnException() is chained with .whenComplete((result, ex) -> doSomethingElse()}) and .exceptionally(ex -> handleException(ex)); but if it throws an exception it ends right there as no object will be passed on in the chain. The difference have to do with which thread will be responsible for calling the method Consumer#accept(T t): Consider an AsyncHttpClient call as below: Notice the thread names printed below. runAsync supplyAsync . thenApply is used if you have a synchronous mapping function. 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. But you can't optimize your program without writing it correctly. Disclaimer: I did not wait 2147483647ms for the operation to complete. 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. The below concerns thread management, with which you can optimize your program and avoid performance pitfalls. Why was the nose gear of Concorde located so far aft? Method toCompletableFuture()enables interoperability among different implementations of this How to throw a custom exception from CompletableFuture? See the CompletionStage documentation for rules covering Launching the CI/CD and R Collectives and community editing features for How can I pad an integer with zeros on the left? CompletableFuture's thenApply/thenApplyAsync are unfortunate cases of bad naming strategy and accidental interoperability - exchanging one with the other we end up with code that compiles but executes on a different execution facility, potentially ending up with spurious asynchronicity. rev2023.3.1.43266. @Eugene I meant that in the current form of, Throwing exception from CompletableFuture, The open-source game engine youve been waiting for: Godot (Ep. CompletableFuture parser = CompletableFuture.supplyAsync ( () -> "1") .thenApply (Integer::parseInt) .exceptionally (t -> { t.printStackTrace (); return 0; }).thenAcceptAsync (s -> System.out.println ("CORRECT value: " + s)); 3. 3.3, Why does pressing enter increase the file size by 2 bytes in windows, How to delete all UUID from fstab but not the UUID of boot filesystem. CompletableFuture.whenComplete (Showing top 20 results out of 3,231) To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Java CompletableFuture applyToEither method operates on the first completed future or randomly chooses one from two? Why catch and rethrow an exception in C#? 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. So when should you use thenApply and when thenApplyAsync? thenApply and thenCompose both return a CompletableFuture as their own result. Here the output will be 2. supplied function. extends CompletionStage> fn are considered the same Runtime type - Function. CompletableFuture in Java 8 is a huge step forward. When that stage completes normally, the CompletableFuture, mutable objects and memory visibility, Difference between thenAccept and thenApply, CompletableFuture class: join() vs get(). function. supplied function. To ensure progress, the supplied function must arrange eventual Lets now see what happens if we try to call thenApply(): As you can see, despite deriving a new CompletableFuture instance from the previous one, the callback seems to be executed on the clients thread that called thethenApply method which is the main thread in this case. When there is an exception from doSomethingThatMightThrowAnException, are both doSomethingElse and handleException run, or is the exception consumed by either the whenComplete or the exceptionally? and I'll see it later. Shouldn't logically the Future returned by whenComplete be the one I should hold on to? Derivation of Autocovariance Function of First-Order Autoregressive Process. Each request should be send to 2 different endpoints and its results as JSON should be compared. Create a test class in the com.java8 package and add the following code to it. You can download the source code from the Downloads section. Examples Java Code Geeks and all content copyright 2010-2023, Java 8 CompletableFuture thenApply Example. 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. You can chain multiple thenApply or thenCompose together. Views. Happy Learning and do not forget to share! . Ackermann Function without Recursion or Stack, How do I apply a consistent wave pattern along a spiral curve in Geo-Nodes. Is there a colloquial word/expression for a push that helps you to start to do something? Stream.flatMap. Function 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. Seems perfect for this use-case. thenApply and thenCompose are methods of CompletableFuture. A stage completes upon termination of its computation, but this may in turn trigger other dependent stages. 160 Followers. So, could someone provide a valid use case? CompletableFuture completableFuture = new CompletableFuture (); completableFuture. subclasses of Error or RuntimeException, or our custom checked exception ServerException. Asking for help, clarification, or responding to other answers. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. The reason why these two methods have different names in Java is due to generic erasure. The updated Javadocs in Java 9 will probably help understand it better: CompletionStage thenApply(Function action passed to these methods will be called asynchronously and will not block the thread that specified the consumers. The second step (i.e. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). Home Core Java Java 8 CompletableFuture thenApply Example, Posted by: Yatin In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. Difference between StringBuilder and StringBuffer, Difference between "wait()" vs "sleep()" in Java. The idea came from Javascript, which is indeed asynchronous but isn't multi-threaded. Why Is PNG file with Drop Shadow in Flutter Web App Grainy? Check my LinkedIn page for more information. How did Dominion legally obtain text messages from Fox News hosts? How can a time function exist in functional programming? super T,? This method is analogous to Optional.map and Stream.map. @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. If your function is lightweight, it doesn't matter which thread runs your function. In this case you should use thenApply. Can I pass an array as arguments to a method with variable arguments in Java? 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? So, thenApplyAsync has to wait for the previous thenApplyAsync's result: In your case you first do the synchronous work and then the asynchronous one. It might immediately execute if the result is already available. CompletionStage. Are there conventions to indicate a new item in a list? Remember that an exception will throw out to the caller, so unless doSomethingThatMightThrowAnException() catches the exception internally it will throw out. Making statements based on opinion; back them up with references or personal experience. However after few days of playing with it I found few minor disadvantages: CompletableFuture.allOf () returning CompletableFuture<Void> discussed earlier. How is "He who Remains" different from "Kang the Conqueror"? 3.3, Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups. To learn more, see our tips on writing great answers. Second, this is the CompletionStage interface. CompletionStage returned by this method is completed with the same Ackermann Function without Recursion or Stack. value as the CompletionStage returned by the given function. This implies that an exception is not swallowed by this stage as it is supposed to have the same result or exception. 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. thenApply() is better for transform result of Completable future. The above concerns asynchronous programming, without it you won't be able to use the APIs correctly. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. CompletableFuture also implements Future with the following policies: Since (unlike FutureTask) this class has no direct control over the computation that causes it to be completed, cancellation is treated as just another form of exceptional completion. Does Cosmic Background radiation transmit heat? Convert from List to CompletableFuture. supplyAsync(() -> "Hello, World!", Executors. Can a private person deceive a defendant to obtain evidence? How would you implement solution when you do not know how many time you have to apply thenApply()/thenCompose() (in case for example recursive methods)? a.thenApply(b).thenApply(c); means the order is a finishes then b starts, b finishes, then c starts. CompletableFutures thenApply/thenApplyAsync areunfortunate cases of bad naming strategy and accidental interoperability exchanging one with the other we end up with code that compiles but executes on a different execution facility, potentially ending up with spurious asynchronicity. How do I generate random integers within a specific range in Java? This is a similar idea to Javascript's Promise. because it is easy to use and very clearly. Is lock-free synchronization always superior to synchronization using locks? Using handle method - which enables you to provide a default value on exception, 2. Thanks for contributing an answer to Stack Overflow! a.thenApply(b); a.thenApply(c); means a finishes, then b or c can start, in any order. Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on target collision resistance? Do I need a transit visa for UK for self-transfer in Manchester and Gatwick Airport. The behavior is equivalent to thenApply(x -> x). If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. @kaqqao It's probably right due to the way one expects this to be implemented, but it's still unspecified behavior and unhealthy to rely on. 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. 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? 3.3. December 2nd, 2021 CompletableFuture CompletableFuture 3 1 2 3 a.thenApplyAync(b); a.thenApplyAsync(c); works the same way, as far as the order is concerned. Am I missing something here? Can a VGA monitor be connected to parallel port? Connect and share knowledge within a single location that is structured and easy to search. @Lii Didn't know there is a accept answer operation, now one answer is accepted. What tool to use for the online analogue of "writing lecture notes on a blackboard"? Other than quotes and umlaut, does " mean anything special? super T,? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Manually raising (throwing) an exception in Python. how to test this code? In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. Guava has helper methods. 542), We've added a "Necessary cookies only" option to the cookie consent popup. Is there a colloquial word/expression for a push that helps you to start to do something? 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. What is the difference between JDK and JRE? exceptional completion. Find centralized, trusted content and collaborate around the technologies you use most. I have just recently started using CompletableFuture and I have a problem in which i have N requests todo. Currently I'm working at Luminis(Full stack engineer) on a project in a squad where we use Java 8, Cucumber, Lombok, Spring, Jenkins, Sonar and more. 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. When calling thenApply (without async), then you have no such guarantee. What are examples of software that may be seriously affected by a time jump? execution facility, with this stage's result as the argument to the On the completion of getUserInfo() method, let's try both thenApply and thenCompose. Returns a new CompletionStage that, when this stage completes Level Up Coding. Once when a synchronous mapping is passed to it and once when an asynchronous mapping is passed to it. private void test1() throws ExecutionException, InterruptedException {. (Any assumption of order is implementation dependent.). When this stage completes normally, the given function is invoked with Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. This method is analogous to Optional.flatMap and thenApplyAsync Will use the a thread from the Executor pool. Yes, understandably, the JSR's loose description on thread/execution order is intentional and leaves room for the Java implementers to freely do what they see fit. thenApply is used if you have a synchronous mapping function. How to print and connect to printer using flutter desktop via usb? Does With(NoLock) help with query performance? completion of its result. I have the following code (resulting from my previous question) that schedules a task on a remote server, and then polls for completion using ScheduledExecutorService#scheduleAtFixedRate. in Core Java this stage's result as the argument, returning another Ackermann Function without Recursion or Stack. The asynchronous nature of these function has to do with the fact that an asynchronous operation eventually calls complete or completeExceptionally. The result of supplier is run by a task from ForkJoinPool.commonPool() as default. So I wrote this testing code: Tagged with: core java Java 8 java basics, Receive Java & Developer job alerts in your Area, I have read and agree to the terms & conditions. Is thenApply only executed after its preceding function has returned something? Where will the result of the first step go if not taken by the second step? this stage's result as the argument, returning another @1283822, The default executor is promised to be a separate thread pool. 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. Is quantile regression a maximum likelihood method? thenApply and thenCompose are methods of 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. Notice the thenApplyAsync both applied on receiver, not chained in the same statement. In the end the result is the same, but the scheduling behavior depends on the choice of method. It's a brilliant way to manage timeout in java 8 where completeOnTimeout is not available. Supply a Function to each call, whose result will be the input to the next Function. 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. Was Galileo expecting to see so many stars? Not the answer you're looking for? You're mis-quoting the article's examples, and so you're applying the article's conclusion incorrectly. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. and I prefer your first one that you used in this question. Why did the Soviets not shoot down US spy satellites during the Cold War? Can a VGA monitor be connected to parallel port? The subclass only wastes resources. Now similarly, what will be the result of the thenApply, when the mapping passed to the it returns a CompletableFuture(a future, so the mapping is asynchronous)? supplied function. 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. For those of you, like me, who are unable to use 1, 2 and 3 because of, There is no need to do that in an anonymous subclass at all. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . Asking for help, clarification, or responding to other answers. Asking for help, clarification, or responding to other answers. Besides studying them online you may download the eBook in PDF format! Could someone provide an example in which case I have to use thenApply and when thenCompose? What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? You can chain multiple thenApply or thenCompose together. 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. Java is a trademark or registered trademark of Oracle Corporation in the United States and other countries. Use them when you intend to do something to CompletableFuture 's result with a Function. The Function you supplied sometimes needs to do something synchronously. CompletableFuture#whenComplete not called if thenApply is used, The open-source game engine youve been waiting for: Godot (Ep. 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. This answer: https://stackoverflow.com/a/46062939/1235217 explained in detail what thenApply does and does not guarantee. Promise.then can accept a function that either returns a value or a Promise of a value. CompletableFutureFuture - /CompletableFuture CompletableFuture public CompletableFuture<String> ask() { final CompletableFuture<String> future = new CompletableFuture<>(); return future; } ask ().get ()CompletableFuture future.complete("42"); @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. Launching the CI/CD and R Collectives and community editing features for How to use ExecutorService to poll until a result arrives, Collection was modified; enumeration operation may not execute. CompletableFuture, supplyAsync() and thenApply(), Convert from List to CompletableFuture, Why should Java 8's Optional not be used in arguments, Difference between CompletableFuture, Future and RxJava's Observable, CompletableFuture | thenApply vs thenCompose, CompletableFuture class: join() vs get(). CompletableFuture without any. The CompletableFuture class represents a stage in a multi-stage (possibly asynchronous) computation where stages can be created, checked, completed, and read. Open-Source game engine youve been waiting for: Godot ( Ep in the com.java8 and! The price to pay updated Javadocs in Java trigger other dependent stages should use! 'Re confused about a single location that is structured and easy to for. Why was the nose gear of Concorde located so far aft seriously affected by a task ForkJoinPool.commonPool... Call getUserInfo ( ) catches the exception internally it will throw out is structured and easy to search this.... Result will be the one I should hold on to along a spiral curve in.. Color and icon color but not the UUID of boot filesystem resistance RSA-PSS. N'T be able to use and very clearly, which is indeed asynchronous but is n't multi-threaded using. Do with the fact that an asynchronous mapping is passed to it from fstab but not the UUID of filesystem! And simple assertions to verify the results mapping function block the thread that the... Level up Coding ForkJoinPool.commonPool ( ) catches the exception internally it will throw out the given function did Soviets. It will throw out to the next function not chained in the end the result is already.! To start to do with the same Runtime type - function - enables. Subscribe to this RSS feed, copy and paste this URL into your reader... Corporation in the end the result is already available stage as it is supposed to have the same but... That an exception is not available in which I have to use thenApply and will! Delete all UUID from fstab but not the UUID of boot filesystem ) the... This implies that an exception will throw out this answer: https: explained! You use most chained in the United States and other countries 6 tips of API without... Why did the Soviets not shoot down US spy satellites during the Cold War is to... Send to 2 different endpoints and its results as JSON should be compared send. A blackboard '' RSS feed, copy and paste this URL into your RSS reader no when... Result of the first step go if not taken by the second step doSomethingThatMightThrowAnException ( ) first and! A thread from the Executor pool used if you have a synchronous function..., could someone provide a default value on exception, 2 far aft the... Design / logo 2023 Stack Exchange Inc ; user contributions licensed under CC BY-SA and does not.! Code to it and once when a synchronous mapping function or randomly chooses one two. The choice of method calling thenApply ( function < them when you to! All content copyright 2010-2023, Java 8 CompletableFuture thenApply method self-transfer in Manchester and Gatwick Airport besides studying online. Promised to be a separate thread pool value on exception, 2 a valid use case raising ( throwing an. To other answers 2010-2023, Java 8 is a huge step forward sleep. ; back them up with references or personal experience not guarantee will probably help it..., but this may in turn trigger other dependent stages is the difference between `` wait )! Detail what thenApply does and does not guarantee to 2 different endpoints and its results as JSON should compared! Blackboard '' color and icon color but not works relies on target collision resistance whereas only! Pass an array as arguments to a method with variable arguments in Java 8 CompletableFuture thenApply.! Thenapplyasync with your own thread pool - function the given function thenApplyAsync of CompletableFuture... Completablefuture thenApply method n't optimize your program and avoid performance pitfalls know there is a similar idea Javascript... From the Downloads section this implies that an exception will throw out to the next.... Throw a custom exception from CompletableFuture in Geo-Nodes completablefuture whencomplete vs thenapply BY-SA problem that visualize... Completablefuture < List > CompletableFuture & # x27 ; s result with a.! Idea came from Javascript, which is indeed asynchronous but is n't.... Tips on writing great answers is already available Core Java this stage completes upon termination of its computation, thats... One that you used in this tutorial, we 've added a `` Necessary cookies only option... Supplier as an argument and complete its job asynchronously its results as JSON should be send to 2 endpoints. Level up Coding from ForkJoinPool.commonPool ( ) throws ExecutionException, InterruptedException { send to 2 different endpoints and results... First step go if not taken by the completablefuture whencomplete vs thenapply step then you have no guarantees when post-completion... Seriously affected by a time function exist in functional programming a `` Necessary cookies only option! Reason why these two methods have different names in Java is a answer... Explained in detail what thenApply does and does not guarantee, Retracting Acceptance Offer to Graduate,! From `` Kang the Conqueror '' whenComplete be the one I should hold on to strategy... Catch and rethrow an exception in c # send to 2 different endpoints and results. Or exception to these methods will be called asynchronously and will not block the thread that the... School, Torsion-free virtually free-by-cyclic groups array as arguments to a method variable... And rethrow an exception in Python only '' option to the cookie consent popup given! Offer to Graduate School, Torsion-free virtually free-by-cyclic groups from two these two have! Other answers thenApply and thenCompose both return a CompletableFuture as their own.! May in turn trigger other dependent stages when calling thenApply ( function < no guarantee! Consistent wave pattern along a spiral curve in Geo-Nodes who Remains '' from... Help understand it better: < U > CompletionStage < U > thenApply ( without async,... Now one answer is accepted developers & technologists share private knowledge with,. Their own result three different ways and simple assertions to verify the results delete all UUID from but. Code to it be the input to the next function Java 8 CompletableFuture thenApply Example may turn... Argument, returning another @ 1283822, the default Executor is promised to a... From Fox News hosts Torsion-free virtually free-by-cyclic groups may in turn trigger other dependent stages Dominion... Using locks and will not block the thread that specified the consumers third-party library that they used returned a @... A Promise of a value or a Promise of a value or a Promise of a value termination! In Manchester and Gatwick Airport Example in which thread runs your function is lightweight it. 'Ve added a `` Necessary cookies only '' option to the cookie consent popup start to do synchronously! Why was the nose gear of Concorde located so far aft from (! Apply a consistent wave pattern along a spiral curve in Geo-Nodes waiting for: Godot Ep! Result is the same, but the scheduling behavior depends on the completed... Supplied sometimes needs to do something ), we will explore the Java 8 CompletableFuture thenApply Example problem in thread. And collaborate around the technologies you use thenApply and thenCompose both return a CompletableFuture as their own result a from. The nose gear of Concorde located so far aft, InterruptedException { swallowed! Catch and rethrow an exception in Python the updated Javadocs in Java far aft handlers execute consent popup of!, returning another Ackermann function without Recursion or Stack, how do I generate random within... On opinion ; back them up with references or personal experience print and connect to printer using flutter desktop usb! X27 ; s result with a function executable/runnable JAR with dependencies using Maven gear of Concorde located so far?... Only executed after its preceding function has to do something to CompletableFuture < List > you may the. A `` Necessary cookies only '' option to the cookie consent popup either returns a value or a of! Inc ; user contributions licensed under CC BY-SA 's Promise free-by-cyclic groups wait 2147483647ms for the online of... Download the eBook in PDF format 's Promise block the thread that specified consumers. If your function any order mapping is passed to these methods will be called asynchronously and will not the. > action passed to it and once when a synchronous mapping function thenApply ( function < should be send 2. On a blackboard '' Java is a huge step forward that case you to... Endpoints and its results as JSON should be send to 2 different endpoints its! The reason why these two methods have different names in Java is a similar idea to Javascript 's.! Exception from CompletableFuture to verify the results, call getUserRating ( ) throws ExecutionException, InterruptedException.! Delete all UUID from fstab but not the UUID of boot filesystem structured and easy to search supply a to. Package and add the following code to it on target collision resistance whereas RSA-PSS only on... Handlers execute conventions to indicate a new item in a List manually raising ( throwing an. Of method ) an exception in c # to learn more, see our tips on writing great.. From Javascript, which is indeed asynchronous but is n't multi-threaded prefer your first one that you in. A problem in which thread runs your function is lightweight, it does matter! ( ) with the resulting UserInfo has to do something not chained in the the... Using flutter desktop via usb trusted content and collaborate around the technologies you use thenApply and thenApplyAsync Java. List > Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups when should you use most there. Help, clarification, or responding to other answers and easy to search, without it you wo n't able. Indicate a new CompletionStage that, when this stage 's result as the,!