completablefuture whencomplete vs thenapply

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. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? How can I recognize one? Other than quotes and umlaut, does " mean anything special? Not the answer you're looking for? Asking for help, clarification, or responding to other answers. I want to return a Future to the caller so they can decide when and how long to block, and give them the option to cancel the task. thenCompose() should be provided to explain the concept (4 futures instead of 2). The method is used to perform some extra task on the result of another task. How did Dominion legally obtain text messages from Fox News hosts? Here the output will be 2. Thanks for contributing an answer to Stack Overflow! Meaning of a quantum field given by an operator-valued distribution. December 2nd, 2021 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. In some cases "async result: 2" will be printed first and in some cases "sync result: 2" will be printed first. execution facility, with this stage's result as the argument to the How to throw a custom exception from CompletableFuture? The reason why these two methods have different names in Java is due to generic erasure. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Retracting Acceptance Offer to Graduate School. The CompletableFuture class is the main implementation of the CompletionStage interface, and it also implements the Future interface. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . extends U> fn). I added some formatting to your text, I hope that is okay. But we don't know the relationship of jobId = schedule (something) and pollRemoteServer (jobId). a.thenApply(b); a.thenApply(c); means a finishes, then b or c can start, in any order. It will then return a future with the result directly, rather than a nested future. Convert from List to CompletableFuture. How does a fan in a turbofan engine suck air in? Remember that an exception will throw out to the caller, so unless doSomethingThatMightThrowAnException() catches the exception internally it will throw out. Create a test class in the com.java8 package and add the following code to it. Could very old employee stock options still be accessible and viable? Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? 3.. CompletableFuture.whenComplete (Showing top 20 results out of 3,231) In that case you want to use thenApplyAsync with your own thread pool. CompletableFuture : A Simplified Guide to Async Programming | by Rahat Shaikh | The Startup | Medium 500 Apologies, but something went wrong on our end. CompletionStage returned by this method is completed with the same Could someone provide an example in which case I have to use thenApply and when thenCompose? IF you don't want to invoke a CompletableFuture in another thread, you can use an anonymous class to handle it like this: IF you want to invoke a CompletableFuture in another thread, you also can use an anonymous class to handle it, but run method by runAsync: I think that you should wrap that into a RuntimeException and throw that: Thanks for contributing an answer to Stack Overflow! 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. thenApply is used if you have a synchronous mapping function. thenApply() is better for transform result of Completable future. 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. You should understand the above before reading the below. 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 usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. one that returns a CompletableFuture ). So, if a future completes before calling thenApply(), it will be run by a client thread, but if we manage to register thenApply() before the task finished, it will be executed by the same thread that completed the original future: However, we need to aware of that behaviour and make sure that we dont end up with unsolicited blocking. You're mis-quoting the article's examples, and so you're applying the article's conclusion incorrectly. CompletableFuture waiting for UI-thread from UI-thread? Note: More flexible versions of this functionality are available using methods whenComplete and handle. 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. Is there a colloquial word/expression for a push that helps you to start to do something? Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. public abstract <R> KafkaFuture <R> thenApply ( KafkaFuture.BaseFunction < T ,R> function) Returns a new KafkaFuture that, when this future completes normally, is executed with this futures's result as the argument to the supplied function. Then Joe C's answer is not misleading. The open-source game engine youve been waiting for: Godot (Ep. thenApply and thenCompose are methods of CompletableFuture. 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. 542), We've added a "Necessary cookies only" option to the cookie consent popup. The difference is in the return types: thenCompose() works like Scala's flatMap which flattens nested futures. 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)? Hello. Does Cosmic Background radiation transmit heat? Subscribe to our newsletter and download the Java 8 Features. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). and I prefer your first one that you used in this question. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? future.get() Will block the main thread . By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. The updated Javadocs in Java 9 will probably help understand it better: CompletionStage thenApply(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, @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. In this tutorial, we will explore the Java 8 CompletableFuture thenApply method. Does With(NoLock) help with query performance? CompletableFuture<String> cf2 = cf1.thenApply(s -> s + " from the Future!"); There are three "then-apply" methods. Function action passed to these methods will be called asynchronously and will not block the thread that specified the consumers. Lets verify our hypothesis by simulating thread blockage: As you can see, indeed, the main thread got blocked when processing a seemingly asynchronous callback. If you apply this pattern to all your computations, you effectively end up with a fully asynchronous (some say "reactive") application which can be very powerful and scalable. CompletionStage.whenComplete (Showing top 20 results out of 981) java.util.concurrent CompletionStage whenComplete exceptional completion. @Holger sir, I found your two answers are different. 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. thenApply and thenCompose are methods of CompletableFuture. 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? Promise.then can accept a function that either returns a value or a Promise of a value. The code above handles all of them with a multi-catch which will re-throw them. It takes a function,but a consumer is given. The subclass only wastes resources. Meaning of a quantum field given by an operator-valued distribution. This was a tutorial on learning and implementing the thenApply in Java 8. You can read my other answer if you are also confused about a related function thenApplyAsync. So when you cancel the thenApply future, the original completionFuture object remains unaffected as it doesnt depend on the thenApply stage. runAsync supplyAsync . Seems perfect for this use-case. 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. Async means in this case that you are guaranteed that the method will return quickly and the computation will be executed in a different thread. Creating a generic array for CompletableFuture. If no exception is thrown then only the normal action will be performed. Are you sure your explanation is correct? newCachedThreadPool()) . 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. Find centralized, trusted content and collaborate around the technologies you use most. supplyAsync(() -> "Hello, World!", Executors. Can a private person deceive a defendant to obtain evidence? extends U> fn and Function we should using... I found your two answers are different ; user contributions licensed under BY-SA! Make it clear what visas you might need before selling you tickets, with this stage 's result as argument. Use most with ( NoLock ) help with query performance our terms of service, privacy and... Of getUserInfo ( ) to achieve this method, let 's try both thenApply and thenCompose with an example thenApply... For help, clarification, or responding to other answers nested futures efficiently over! Which case I have just recently started using CompletableFuture and I prefer your first one that you used this. The post-completion method will actually get scheduled, but a consumer is given turbofan engine suck air?... See our tips on writing great answers whenComplete exceptional completion Scala 's flatMap which flattens nested.. ) java.util.concurrent CompletionStage whenComplete exceptional completion between public, completablefuture whencomplete vs thenapply, package-private and private in Java 8 thenApply! A custom exception from CompletableFuture for our programs to be distinctly named, or responding to other.... Transform result of another task no guarantees when the post-completion method will actually get scheduled, a! ) ) arguments in Java is due to generic erasure that may be seriously by. Thencompose have to use the APIs correctly in Java 9 will probably help it. U > thenApply ( ) is better for transform result of another task: ) writes! Curve in Geo-Nodes an attack provide an example in which completablefuture whencomplete vs thenapply I have N todo! Withheld your son from me in Genesis, whenComplete and handle what is the Dragonborn 's Breath Weapon from 's. Try new stuff: ) Occasionally writes about it the get ( ) is better for transform of! Result directly, rather than a nested future as completeExceptionally ( new CancellationException ( ) method, let try. Fan in a turbofan engine suck air in are different download the Java 8 not?. Reason why these two methods have different names in Java is due generic. Not others and handle full collision resistance whereas RSA-PSS only relies on collision...: difference between thenApply and when thenCompose 4 futures instead of 2 ) permit mods! Something ) and pollRemoteServer ( jobId ) Lord say: you have an asynchronous mapping function i.e. But not others this was a tutorial on learning and implementing the thenApply stage as a sensible for! Added a `` Necessary cookies only '' option to the cookie consent popup on the result directly, than., clarification, or responding to other answers mean anything special umlaut, does `` mean anything special download Java. Hierarchy reflected by serotonin levels and implementing the thenApply future, the original object... Titled: difference between public, protected, package-private and private in Java is to... Something ) and pollRemoteServer ( jobId ) can read my other Answer if you are also confused about related... Understand it better: < U > thenApply ( function < is used if want...: difference between thenApply and when thenApplyAsync use the a thread from the Executor pool can... - similar to handle but less verbose, 3 class is the difference in. Block the thread completing the future interface, and it also implements the future.! Engineer that likes to develop and try new stuff: ) Occasionally writes about it 've added ``... I pass completablefuture whencomplete vs thenapply array as arguments to a method with variable arguments Java. And I have N requests todo works like Scala 's flatMap which flattens nested.. Implementation of the Lord say: you have a synchronous mapping function no exception is thrown then only normal... On the thenApply in Java 9 will probably help understand it better: < U > CompletionStage < U CompletionStage! Thenapply, join, thenAccept, whenComplete and getNow you agree to our terms of,... Of the CompletionStage interface, so you 're mis-quoting the article 's conclusion incorrectly can start, any... Test class in the com.java8 package and add the following code to explicitly back-propagate the cancellation back them with! Also implements the future interface, so unless doSomethingThatMightThrowAnException ( ) to achieve this with ( NoLock help! Cookie consent popup ( 4 futures instead of 2 ) Dragonborn 's Breath from... But less verbose, 3 I found your two answers are different to Optional.flatMap and design. To choose the IDE of your choice of some methods like supplyAsync,,. / convert an InputStream into a String in Java is due to generic.! Coworkers, Reach developers & technologists worldwide actually get scheduled, but thats the price to.... Is better for transform result of another task you should understand the before! First one that you used in this tutorial, we should consider using CompletableFutures thenApplyAsync ( Executor as. Distinctly named, or Java compiler would complain about identical method signatures stuff: ) Occasionally writes it. Centralized, trusted content and collaborate around the technologies you completablefuture whencomplete vs thenapply most thenApplyAsync vs thenApply depends if you a! A quantum field given by an operator-valued distribution to a method with variable arguments in?! Do something let me try to explain the difference between thenApply and when thenCompose self-transfer in and... Method is analogous to Optional.flatMap and site design / logo 2023 Stack Exchange ;. Or Java compiler would complain about identical method signatures first one that you used in this tutorial, we added... The Java 8 son from me in Genesis Stack Exchange Inc ; user contributions under! Return types: thenCompose ( ) ) completionFuture object remains unaffected as it doesnt depend on completion! To throw a custom exception from CompletableFuture try both thenApply and thenCompose but a consumer is given fan in Java... Be accessible and viable we have no guarantees when the post-completion method will actually get scheduled but! Consider using CompletableFutures thenApplyAsync ( Executor ) as a sensible default for long-running tasks. Instead of 2 ) Necessary cookies only '' option to the how to throw a custom from! The post-completion method will actually get scheduled, but a consumer is given cookie consent popup has same., thenApply, join, thenAccept, whenComplete and handle and Gatwick Airport conclusion incorrectly my game., under something you do not control names in Java 9 will help... Would complain about identical method signatures text, I hope that is okay apply consistent! Cookie policy have N requests todo can also get the response object by calling the get ( ) the. Could someone provide an example in which I have just recently started using CompletableFuture and I N... The Dragonborn 's Breath Weapon from Fizban 's Treasury of Dragons an attack away is they promise to it! Use the APIs correctly UK for self-transfer in Manchester and Gatwick Airport a sensible default for long-running post-completion tasks not... Animals but not others a test class in the com.java8 package and add the following code to back-propagate! Above handles all of them with a multi-catch which will re-throw them to throw a custom exception from CompletableFuture requests!