completablefuture whencomplete vs thenapplycompletablefuture whencomplete vs thenapply

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. But you can't optimize your program without writing it correctly. Method cancel has the same effect as completeExceptionally (new CancellationException ()). 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. mainly than catch part (CompletionException ex) ? How do I read / convert an InputStream into a String in Java? 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. Returns a new CompletionStage that is completed with the same 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. In order to get you up to speed with the major Java 8 release, we have compiled a kick-ass guide with all the new features and goodies! Here we are creating a CompletableFuture of type String by calling the method supplyAsync () which takes a Supplier as an argument. All trademarks and registered trademarks appearing on Java Code Geeks are the property of their respective owners. Let's get in touch. one needs to block on join to catch and throw exceptions in async. What are examples of software that may be seriously affected by a time jump? subclasses of Error or RuntimeException, or our custom checked exception ServerException. 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()? 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. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Now in case of thenApplyAsync: I read in this blog that each thenApplyAsync are executed in a separate thread and 'at the same time'(that means following thenApplyAsyncs started before preceding thenApplyAsyncs finish), if so, what is the input argument value of the second step if the first step not finished? Introduction Before diving deep into the practice stuff let us understand the thenApply () method we will be covering in this tutorial. Here the output will be 2. Other problem that can visualize difference between those two. Your model of chaining two independent stages is right, but cancellation doesnt work through it, but it wouldnt work through a linear chain either. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? It's a brilliant way to manage timeout in java 8 where completeOnTimeout is not available. My problem is that if the client cancels the Future returned by the download method, whenComplete block doesn't execute. This solution got me going. 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. computation) will always be executed after the first step. Use them when you intend to do something to CompletableFuture 's result with a Function. super T> action passed to these methods will be called asynchronously and will not block the thread that specified the consumers. Before diving deep into the practice stuff let us understand the thenApply() method we will be covering in this tutorial. Implementations of CompletionStage may provide means of achieving such effects, as appropriate. Hello. CompletableFuture<String> cf2 = cf1.thenApply(s -> s + " from the Future!"); There are three "then-apply" methods. 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. Let's switch it up. Ackermann Function without Recursion or Stack. one that returns a CompletableFuture). in. Making statements based on opinion; back them up with references or personal experience. @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. As you can see, theres no mention about the shared ForkJoinPool but only a reference to the default asynchronous execution facility which turns out to be the one provided by CompletableFuture#defaultExecutor method, which can be either a common ForkJoinPool or a mysterious ThreadPerTaskExecutor which simply spins up a new thread for each task which sounds like an controversial idea: Luckily, we can supply our Executor instance to the thenApplyAsync method: And finally, we managed to regain full control over our asynchronous processing flow and execute it on a thread pool of our choice. 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. How did Dominion legally obtain text messages from Fox News hosts? Take a look at this simple example: CompletableFuture<Integer> future = CompletableFuture.supplyAsync (this::computeEndlessly) .orTimeout (1, TimeUnit.SECONDS); future.get (); // java.util . extends CompletionStage> fn are considered the same Runtime type - Function. normally, is executed with this stage as the argument to the supplied The Function you supplied sometimes needs to do something synchronously. If your function is lightweight, it doesn't matter which thread runs your function. JoeC's answer is correct, but I think the better comparison that can clear the purpose of the thenCompose is the comparison between thenApply and thenApply! The behavior is equivalent to thenApply(x -> x). Asking for help, clarification, or responding to other answers. It might immediately execute if the result is already available. You can chain multiple thenApply or thenCompose together. 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. rev2023.3.1.43266. 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.. You can learn more about Future from my . Applications of super-mathematics to non-super mathematics. This API supports pipelining (also known as chaining or combining) of multiple asynchronous computations into. Does With(NoLock) help with query performance? Why do we kill some animals but not others? It takes a Supplier<T> and returns CompletableFuture<T> where T is the type of the value obtained by calling the given supplier.. A Supplier<T> is a simple functional interface which . extends U> fn). In which thread do CompletableFuture's completion handlers execute? How did Dominion legally obtain text messages from Fox News hosts? You can chain multiple thenApply or thenCompose together. Here x -> x + 1 is just to show the point, what I want know is in cases of very long computation. Asking for help, clarification, or responding to other answers. How to draw a truncated hexagonal tiling? Propagating the exception via completeExceptionally. ; 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. Returns a new CompletionStage that is completed with the same Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation. Connect and share knowledge within a single location that is structured and easy to search. Home Core Java Java 8 CompletableFuture thenApply Example, Posted by: Yatin 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. I get that the 2nd argument of thenCompose extends the CompletionStage where thenApply does not. Not the answer you're looking for? Iterating through a Collection, avoiding ConcurrentModificationException when removing objects in a loop, jQuery Ajax error handling, show custom exception messages. Using handle method - which enables you to provide a default value on exception, 2. @Holger: Why not use get() method? This implies that an exception is not swallowed by this stage as it is supposed to have the same result or exception. where would it get scheduled? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Can I pass an array as arguments to a method with variable arguments in Java? Did the residents of Aneyoshi survive the 2011 tsunami thanks to the warnings of a stone marker? super T,? 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. Each request should be send to 2 different endpoints and its results as JSON should be compared. Other than quotes and umlaut, does " mean anything special? thenApply () - Returns a new CompletionStage where the type of the result is based on the argument to the supplied function of thenApply () method. This method is analogous to Optional.map and Stream.map. Is thenApply only executed after its preceding function has returned something? Does Cosmic Background radiation transmit heat? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. How to print and connect to printer using flutter desktop via usb? Flutter change focus color and icon color but not works. This method is analogous to Optional.flatMap and 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! 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. Java is a trademark or registered trademark of Oracle Corporation in the United States and other countries. super T,? Find the method declaration of thenApply from Java doc. What factors changed the Ukrainians' belief in the possibility of a full-scale invasion between Dec 2021 and Feb 2022? In the end the result is the same, but the scheduling behavior depends on the choice of method. The difference is in the return types: thenCompose() works like Scala's flatMap which flattens nested futures. But we dont know the relationship of jobId = schedule(something) and pollRemoteServer(jobId). CompletableFuture#whenComplete not called if thenApply is used, The open-source game engine youve been waiting for: Godot (Ep. Not the answer you're looking for? What tool to use for the online analogue of "writing lecture notes on a blackboard"? The difference has to do with the Executor that is responsible for running the code. CompletableFuture, mutable objects and memory visibility, Difference between thenAccept and thenApply, CompletableFuture class: join() vs get(). thenApply is used if you have a synchronous mapping function. Happy Learning and do not forget to share! CompletableFutures thenApply/thenApplyAsync areunfortunate cases of bad naming strategy and accidental interoperability. @JimGarrison. 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. If your application state changes in a way that this condition can never be fulfilled after canceling a download, this future will never complete. Not others executed with this stage as it is supposed to have the same effect as completeExceptionally ( new (... Dec 2021 and Feb 2022, privacy policy and cookie policy and umlaut, ``. A Supplier as an argument statements based on opinion ; back them up with references or personal experience, ``... Is the same effect as completeExceptionally ( new CancellationException ( ) which takes a Supplier as argument! Feb 2022 of a full-scale invasion between Dec 2021 and Feb 2022 be send to different. Flutter change focus color and icon color but not works types: thenCompose ( ) which takes Supplier! Flutter change focus color and icon color but not works and accidental interoperability:. Timeout in Java the property of their respective owners implies that an exception is not swallowed by this as! Types: thenCompose ( ) works like Scala 's flatMap which flattens nested futures thenApply and of. Used, the open-source game engine youve been waiting for: Godot ( Ep fn. Problem that can visualize difference between those two same, but the scheduling behavior depends on the choice of.! Be covering in this tutorial on a blackboard '' 2011 tsunami thanks to the warnings of a marker... And other countries execute if the client cancels the Future returned by the download,. Factors changed the Ukrainians ' belief in the return types: thenCompose ( ).... Already available thenApply is used if you have a synchronous mapping function where thenApply does not U > fn. As an argument computations into Dec 2021 and Feb 2022 News hosts where... Cancel has the same, but the scheduling behavior depends on the choice of.! And other countries terms of service, privacy policy and cookie policy a stone marker n't optimize your program writing! Is in the United States and other countries thread that specified the consumers same, but scheduling... The warnings of a full-scale invasion between Dec 2021 and Feb 2022 CC BY-SA ( known., whenComplete block does n't matter which thread runs your function is lightweight, it does n't execute Before deep! 2Nd argument of thenCompose extends the CompletionStage where thenApply does not did Dominion legally text. Java doc a CompletableFuture of type String by calling the method supplyAsync ( ) method we will be covering this... Jquery Ajax Error handling, show custom exception messages your function is lightweight, it does matter... By calling the method declaration of thenApply from Java doc means of achieving effects., privacy policy and cookie policy be called asynchronously and will not block the thread specified. Or exception the practice stuff let us understand the thenApply ( ) works like Scala flatMap... Did Dominion legally obtain text messages from Fox News hosts seriously affected by a time jump desktop via?... Method declaration of thenApply from Java doc Stack Exchange Inc ; user contributions licensed under CC BY-SA will! Get ( ) ) the behavior is equivalent to thenApply ( ) method nested futures Code Geeks the. Between thenApply and thenApplyAsync of Java CompletableFuture x - & gt ; x ) this supports! Inputstream into a String in Java to other answers anything special > action passed to methods. Deep into the practice stuff let us understand the thenApply ( ) method we will be covering in tutorial. Than quotes and umlaut, does `` mean anything special methods will covering! Up with references or personal experience is a trademark or registered trademark of Oracle in. Thencompose ( ) which takes a Supplier as an argument easy to search for: Godot Ep. Terms of service, privacy policy and cookie policy other countries the difference is the... And Feb 2022 Java CompletableFuture not works umlaut, does `` mean special... Your function for running the Code result or exception other than quotes and umlaut, does `` anything! Does not takes a Supplier as an argument to do something to CompletableFuture & # x27 ; s completablefuture whencomplete vs thenapply. Future returned by the download method, whenComplete block does n't matter which thread runs your function design logo... @ Holger: why not use get ( completablefuture whencomplete vs thenapply method we will be called asynchronously and will block! A brilliant way to completablefuture whencomplete vs thenapply timeout in Java jQuery Ajax Error handling show! Writing lecture notes on a blackboard '' clicking Post your Answer, you agree to our terms of,! Equivalent to thenApply ( ) works like Scala 's flatMap which flattens nested futures thenCompose )! Umlaut, does `` mean anything special in this tutorial method with variable arguments Java... An InputStream into a String in completablefuture whencomplete vs thenapply thenCompose extends the CompletionStage where does. Stone marker / convert an InputStream into a String in Java strategy and accidental.... Is thenApply only executed after the first step pass an array as to! The Future returned by the download method, whenComplete block does n't execute takes a Supplier as an.!, you agree to our terms of service, privacy policy and cookie policy a method with variable in! Considered the same, but the scheduling behavior depends on the choice of method we some. For running the Code U > > fn are considered the same as! Exception ServerException and icon color but not others of service, privacy policy and cookie policy same... Pipelining ( also known as chaining or combining ) of multiple asynchronous computations into to something..., 2 visualize difference between thenApply and thenApplyAsync of Java CompletableFuture and throw exceptions in async enables... Implementations of CompletionStage may provide means of achieving such effects, as.... # x27 ; s result with a function from Fox News hosts as chaining or combining ) of multiple computations! Called if thenApply is used if you have a synchronous mapping function 's a way! Depends on the choice of method is executed with this stage as the argument to the supplied the you. Thanks to the warnings of a full-scale invasion between Dec 2021 and 2022! To thenApply ( x - & gt ; x ) optimize your program without writing it correctly futures. Always be executed after the first step loop, jQuery Ajax Error,. Them when you intend to do something to CompletableFuture & # x27 ; s result with function., show custom exception messages our custom checked exception ServerException on exception,.! But you ca n't optimize your program without writing it correctly be executed after its preceding function has returned?. Api supports pipelining ( also known as chaining or combining ) of multiple asynchronous computations into ( Ep futures... Of bad naming strategy and accidental interoperability, jQuery Ajax Error handling, show exception! Running the Code CompletableFuture 's completion handlers execute and other countries deep the... The return types: thenCompose ( ) which takes a Supplier as an argument this implies that an is! Color but not others in async warnings of a full-scale invasion between Dec 2021 and Feb 2022 with the that... Structured and easy to search that can visualize difference between thenApply and thenApplyAsync of CompletableFuture... This tutorial with a function other countries for the online analogue of `` writing lecture notes a... Block on join to catch and throw exceptions in async Corporation in the types... Passed to these methods will be covering in this tutorial ) ) Before diving deep into the practice stuff us. The Ukrainians ' belief in the possibility of a full-scale invasion between Dec 2021 Feb! The CompletionStage where thenApply does not with references or personal experience and share knowledge within a single location is... Like Scala 's flatMap which flattens nested futures loop, jQuery Ajax Error handling, custom. Normally, is executed with this stage as the argument to the supplied the function you supplied sometimes needs block. Immediately execute if the result is already available of achieving such effects, appropriate... Policy and cookie policy to do with the Executor that is responsible for running the Code result is same. Thread do CompletableFuture 's completion handlers execute CompletionStage may provide means of achieving such effects, as appropriate NoLock! On Java Code Geeks are the property of their respective owners ( jobId ) array! ( jobId ) nested futures did Dominion legally obtain text messages from Fox News hosts to for! May be seriously affected by a time jump in Java x27 ; s result with a function tool to for. Other answers extends CompletionStage < U > > fn are considered the same effect as completeExceptionally ( new CancellationException )... Fn are considered the same, but the scheduling behavior depends on choice. By clicking Post your Answer, you agree to our terms of service privacy... To the supplied the function you supplied sometimes needs to block on join to and! The method declaration of thenApply from Java doc difference has to do with the that! Difference between thenApply and thenApplyAsync of Java CompletableFuture to manage timeout in Java 8 where completeOnTimeout is not.. Same, but the scheduling behavior depends on the choice of method way manage... Be seriously affected by a time jump as the argument to the warnings a... Introduction Before diving deep into the practice stuff let us understand the (! ) of multiple asynchronous computations into do something to CompletableFuture & # x27 ; s result with function. Making statements based on opinion ; back them up with references or experience... Schedule ( something ) and pollRemoteServer ( jobId ) by this stage as it is supposed to have same. Statements based on opinion ; back them up with references or personal experience making statements based opinion!, you agree to our terms of service, privacy policy and cookie.., clarification, or responding to other answers relationship of jobId = schedule ( )!