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. 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. What tool to use for the online analogue of "writing lecture notes on a blackboard"? super T,? super T,? Then Joe C's answer is not misleading. 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. Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? Thanks for contributing an answer to Stack Overflow! private void test1() throws ExecutionException, InterruptedException {. 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. a.thenApply(b).thenApply(c); means the order is a finishes then b starts, b finishes, then c starts. Implementations of CompletionStage may provide means of achieving such effects, as appropriate. execution facility, with this stage's result as the argument to the What does "Could not find or load main class" mean? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? Let me try to explain the difference between thenApply and thenCompose with an example. CompletableFuture.thenApply is inherited from CompletionStage. In that case you should use thenCompose. Then Joe C's answer is not misleading. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Asking for help, clarification, or responding to other answers. Could someone provide an example in which case I have to use thenApply and when thenCompose? Function CompletionStage thenApply(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. I can't get my head around the difference between thenApply and thenCompose. CompletableFuture is a class that implements two interface.. First, this is the Future interface. thenApply and thenCompose both return a CompletableFuture as their own result. It's abhorrent and unreadable, but it works and I couldn't find a better way: I've discovered tascalate-concurrent, a wonderful library providing a sane implementation of CompletionStage, with support for dependent promises (via the DependentPromise class) that can transparently back-propagate cancellations. 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. My understanding is that through the results of the previous step, if you want to perform complex orchestration, thenCompose will have an advantage over thenApply. The result of supplier is run by a task from ForkJoinPool.commonPool() as default. Do flight companies have to make it clear what visas you might need before selling you tickets? 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. Function(a future, so the mapping is asynchronous)? thenCompose( s -> callSync (() -> s), null); with the callSync -method being: Code (Java): 542), We've added a "Necessary cookies only" option to the cookie consent popup. What are some tools or methods I can purchase to trace a water leak? To learn more, see our tips on writing great answers. Maybe I didn't understand correctly. This method is analogous to Optional.map and Stream.map. Supply a Function to each call, whose result will be the input to the next Function. 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. The usage of thenApplyAsync vs thenApply depends if you want to block the thread completing the future or not. But we don't know the relationship of jobId = schedule (something) and pollRemoteServer (jobId). Method toCompletableFuture()enables interoperability among different implementations of this Flutter change focus color and icon color but not works. With CompletableFuture you can also register a callback for when the task is complete, but it is different from ListenableFuture in that it can be completed from any thread that wants it to complete. thenCompose() should be provided to explain the concept (4 futures instead of 2). Other than quotes and umlaut, does " mean anything special? Do German ministers decide themselves how to vote in EU decisions or do they have to follow a government line? This was a tutorial on learning and implementing the thenApply in Java 8. By leveraging functional programming, Principal Engineer at Mi|iM, ex-Lead Architect at HazelcastFollow @pivovarit. You can chain multiple thenApply or thenCompose together. thenApply and thenCompose are methods of CompletableFuture. 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. The function may be invoked by the thread that calls thenApply or it may be invoked by the thread that . You can read my other answer if you are also confused about a related function thenApplyAsync. In that case you want to use thenApplyAsync with your own thread pool. To start, there is nothing in thenApplyAsync that is more asynchronous than thenApply from the contract of these methods. ; 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. Why was the nose gear of Concorde located so far aft? Why did the Soviets not shoot down US spy satellites during the Cold War? This method returns a new CompletionStage that, when this stage completes with exception, is executed with this stage's exception as the argument to the supplied function. Is there a colloquial word/expression for a push that helps you to start to do something? CompletableFuture waiting for UI-thread from UI-thread? How do I efficiently iterate over each entry in a Java Map? thenApply () - Returns a new CompletionStage where the type of the result is based on the argument to the supplied function of thenApply () method. supplied function. Kiskae I just ran this experiment calling thenApply on a CompletableFuture and thenApply was executed on a different thread. Ackermann Function without Recursion or Stack. The open-source game engine youve been waiting for: Godot (Ep. the third step will take which step's result? By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. @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. thenCompose() should be provided to explain the concept (4 futures instead of 2). CompletableFuture.supplyAsync(): On contrary to the above use-case, if we want to run some background task asynchronously and want to return anything from that task, we should use CompletableFuture.supplyAsync(). 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. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? 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. Imo you can just use a completable future: Code (Java): CompletableFuture < String > cf = CompletableFuture . 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! When and how was it discovered that Jupiter and Saturn are made out of gas? @Holger sir, I found your two answers are different. Connect and share knowledge within a single location that is structured and easy to search. What is the difference between thenApply and thenApplyAsync of Java CompletableFuture? We want to call getUserInfo() first, and on its completion, call getUserRating() with the resulting UserInfo. Other problem that can visualize difference between those two. I honestly thing that a better code example that has BOTH sync and async functions with BOTH .supplyAsync().thenApply() and .supplyAsync(). rev2023.3.1.43266. Check my LinkedIn page for more information. What are some tools or methods I can purchase to trace a water leak? 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. The above concerns asynchronous programming, without it you won't be able to use the APIs correctly. Does java completableFuture has method returning CompletionStage to handle exception? JCGs (Java Code Geeks) is an independent online community focused on creating the ultimate Java to Java developers resource center; targeted at the technical architect, technical team lead (senior developer), project manager and junior developers alike. Yurko. I changed my code to explicitly back-propagate the cancellation. What factors changed the Ukrainians' belief in the possibility of a full-scale invasion between Dec 2021 and Feb 2022? All trademarks and registered trademarks appearing on Java Code Geeks are the property of their respective owners. Asking for help, clarification, or responding to other 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. Returns a new CompletionStage that is completed with the same Is there a way to only permit open-source mods for my video game to stop plagiarism or at least enforce proper attribution? The return type of your Function should be a CompletionStage. 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. 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. . completion of its result. Examples Java Code Geeks is not connected to Oracle Corporation and is not sponsored by Oracle Corporation. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. The article's conclusion does not apply because you mis-quoted it. This implies that an exception is not swallowed by this stage as it is supposed to have the same result or exception. The reason why these two methods have different names in Java is due to generic erasure. How do I declare and initialize an array in Java? The take away is that for thenApply, the runtime promises to eventually run your function using some executor which you do not control. 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. CompletionStage. Launching the CI/CD and R Collectives and community editing features for CompletableFuture | thenApplyAsync vs thenCompose and their use cases. Could someone provide an example in which case I have to use thenApply and when thenCompose? What are the differences between a HashMap and a Hashtable in Java? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Why was the nose gear of Concorde located so far aft? 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. To learn more, see our tips on writing great answers. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Level Up Coding. It's obvious I'm misunderstanding something about Future composition What should I change? CompletableFuture.supplyAsync supplyAsync accepts a Supplier as an argument and complete its job asynchronously. whenCompletewhenCompleteAsync 2.1whenComplete whenComplete ()BiConsumerBiConsumeraccept (t,u)future @Test void test() throws ExecutionException, InterruptedException { System.out.println("test ()"); On the completion of getUserInfo() method, let's try both thenApply and thenCompose. 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. Find centralized, trusted content and collaborate around the technologies you use most. Why did the Soviets not shoot down US spy satellites during the Cold War? To learn more, see our tips on writing great answers. Stream.flatMap. When and how was it discovered that Jupiter and Saturn are made out of gas? It will then return a future with the result directly, rather than a nested future. 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. In some cases "async result: 2" will be printed first and in some cases "sync result: 2" will be printed first. You can read my other answer if you are also confused about a related function thenApplyAsync. Thus thenApply and thenCompose have to be distinctly named, or Java compiler would complain about identical method signatures. What is the difference between public, protected, package-private and private in Java? When we re-throw the cause of the CompletionException, we may face unchecked exceptions, i.e. thenApply is used if you have a synchronous mapping function. The Function you supplied sometimes needs to do something synchronously. Is the Dragonborn's Breath Weapon from Fizban's Treasury of Dragons an attack? I added some formatting to your text, I hope that is okay. For our programs to be predictable, we should consider using CompletableFutures thenApplyAsync(Executor) as a sensible default for long-running post-completion tasks. When this stage completes normally, the given function is invoked with 3.3. What tool to use for the online analogue of "writing lecture notes on a blackboard"? What is the difference between public, protected, package-private and private in Java? thenApplyAsync Will use the a thread from the Executor pool. Let's switch it up. function. CompletionStage.whenComplete (Showing top 20 results out of 981) java.util.concurrent CompletionStage whenComplete 6 Tips of API Documentation Without Hassle Using Swagger (OpenAPI) + Spring Doc. Otherwise, if this stage completes normally, then the returned stage also completes normally with the same value. This is a similar idea to Javascript's Promise. Why does RSASSA-PSS rely on full collision resistance whereas RSA-PSS only relies on target collision resistance? thread pool), <---- do you know which default Thread Pool is that? The difference has to do with the Executor that is responsible for running the code. 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. If your function is heavy CPU bound, you do not want to leave it to the runtime. I only write it up in my mind. The result of supplier is run by a task from ForkJoinPool.commonPool () as default. 3.3, Retracting Acceptance Offer to Graduate School, Torsion-free virtually free-by-cyclic groups. Here it makes a difference because both call 1 and 2 can run asynchronously, call 1 on a separate thread and call 2 on some other thread, which might be the main thread. To ensure progress, the supplied function must arrange eventual Why does the Angel of the Lord say: you have not withheld your son from me in Genesis? Asking for help, clarification, or responding to other answers. I am using JetBrains IntelliJ IDEA as my preferred IDE. Why is executing Java code in comments with certain Unicode characters allowed? What is a case where `thenApply()` vs. `thenCompose()` is ambiguous despite the return type of the lambda? Here we are creating a CompletableFuture of type String by calling the method supplyAsync () which takes a Supplier as an argument. Using whenComplete Method - using this will stop the method on its tracks and not execute the next thenAcceptAsync Each operator on CompletableFuture generally has 3 versions. The idea came from Javascript, which is indeed asynchronous but isn't multi-threaded. forcibly completing normally or exceptionally, probing completion status or results, or awaiting completion of a stage. computation) will always be executed after the first step. extends CompletionStage> fn are considered the same Runtime type - Function. This method is analogous to Optional.map and Stream.map. Hello. 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. 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 to draw a truncated hexagonal tiling? Asking for help, clarification, or responding to other answers. I must point out that the people who wrote the JSR must have confused the technical term "Asynchronous Programming", and picked the names that are now confusing newcomers and veterans alike. Connect and share knowledge within a single location that is structured and easy to search. 3.. Not the answer you're looking for? normally, is executed with this stage as the argument to the supplied You can achieve your goal using both techniques, but one is more suitable for one use case then other. 1.2 CompletableFuture . Weapon damage assessment, or What hell have I unleashed? Does Cosmic Background radiation transmit heat? rev2023.3.1.43266. On the completion of getUserInfo() method, let's try both thenApply and thenCompose. Before diving deep into the practice stuff let us understand the thenApply() method we will be covering in this tutorial. We want to call getUserInfo() first, and on its completion, call getUserRating() with the resulting UserInfo. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. The following is an example of an asynchronous operation that calls a Amazon DynamoDB function to get a list of tables, receiving a CompletableFuture that can hold a ListTablesResponse object. Where will the result of the first step go if not taken by the second step? Returns a new CompletableFuture that is completed when this CompletableFuture completes, with the result of the given function of the exception triggering this CompletableFuture's completion when it completes exceptionally; otherwise, if this CompletableFuture completes normally, then the returned CompletableFuture also completes normally with the same value. Does Cosmic Background radiation transmit heat? thenApply and thenCompose both return a CompletableFuture as their own result. But when the thenApply stage is cancelled, the completionFuture still may get completed when the pollRemoteServer (jobId).equals ("COMPLETE") condition is fulfilled, as that polling doesn't stop. I use the following rule of thumb: In both thenApplyAsync and thenApply the Consumer fn). 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. Which part of throwing an Exception is expensive? If the mapping passed to the thenApply returns an String(a non-future, so the mapping is synchronous), then its result will be CompletableFuture. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. An argument one from two thenApplyAsync will use the a thread from the of! With an example of achieving such effects, as appropriate probing completion status or results, or what hell I. ) an exception in Python call, whose result will be the input to runtime! We 've added a `` Necessary cookies only '' option to the runtime promises to eventually run your should... Future interface let US understand the thenApply stage and other countries and icon color not! Both thenApply and thenCompose both return a CompletableFuture and thenApply the Consumer < the practice stuff let US understand thenApply. That for thenApply, the original completionFuture object remains unaffected as it is supposed to have same. Meaning of a stage to your text, I found your two answers are different I 'm something. Government line it may be invoked by the thread that complain about identical signatures... Is a high-level API for asynchronous programming in Java 8 it does n't matter which do! To eventually run your function is lightweight, it does n't matter which thread do CompletableFuture 's result of! Sensible default for long-running post-completion tasks sponsored by Oracle Corporation a water leak that can visualize difference thenApply... You wo n't be able to use thenApply and thenCompose with an example in case! Icon color but not works terms of service, privacy policy and cookie policy object remains unaffected as is. Has to do something to CompletableFuture 's result call getUserInfo ( ) enables interoperability different... Between those two does n't matter which thread runs your function you are also confused about without. Full collision resistance '' option to the runtime promises to eventually run your function is heavy CPU,! That likes to develop and try new stuff: ) Occasionally writes about it thenApplyAsync. Input, thus unwrapping the CompletionStage by leveraging functional programming, Principal Engineer at Mi|iM, Architect! Step 's result Async variants to have the same value change focus color and icon color but not.. Completionstage may provide means of achieving such effects, as appropriate only on! Will take which step 's result and collaborate around the difference between public, protected package-private... To Oracle Corporation in the return types completablefuture whencomplete vs thenapply thenCompose ( ) method, let 's try both thenApply and of... Thread that not connected to Oracle Corporation in the United States and countries! To other answers thread runs your function using some Executor which you do want... And Feb 2022 has to do something synchronously @ Holger sir, I found your two are. < -- -- do you know which default thread pool is that for thenApply the! By an operator-valued distribution flight companies have to follow a government line the Ukrainians ' in! To your text, I hope that is responsible for running the.... That implements two interface.. first, and on its completion, call getUserRating ( as!, if a third-party library that they used returned a, @ Holger sir, I your. For asynchronous programming in Java online analogue of `` writing lecture notes on a different thread in thenApplyAsync... Answer if you get a timeout, you agree to our terms of service, policy! Code Geeks are the differences between a HashMap and a Hashtable in Java collaborate around the you... Is a high-level API for asynchronous programming, Principal Engineer at Mi|iM ex-Lead. Is a class that implements two interface.. first, and on its completion, call (. Should be provided to explain the concept ( 4 futures instead of 2 ) start to do something synchronously spy... Help with query performance compiler would complain about identical method signatures an?! Location that is responsible for running the code, privacy policy and cookie policy to... The ones already completed I unleashed when thenCompose names in Java both function can start once completablefuture whencomplete vs thenapply completes in. On a blackboard '' extends CompletionStage < U > > fn are considered the same result or exception as.. My preferred IDE step will take which step 's result new CompletableFuture ( ) as default timeout, you to..., probing completion status or results, or responding to other answers will always executed! Breath Weapon from Fizban 's Treasury of Dragons an attack the Ukrainians ' in! High-Level API for asynchronous programming in Java hell have I unleashed means function. Sir, I found your two answers are different may provide means achieving. And try new stuff: ) Occasionally writes about it that likes develop., this is the difference has to do something to CompletableFuture 's completion handlers?! We re-throw the cause of the CompletionException, we may face unchecked exceptions, i.e is. On full collision resistance and thenCompose with an example in which case I have to be distinctly named or! Privacy policy and cookie policy apply because you mis-quoted it great answers when?. It may be invoked by the thread completing the future returned by whenComplete be the to! Interoperability among different implementations of this Flutter change focus color and icon color but not works other! Apis correctly CompletableFuture and thenApply was executed on a different thread these two methods have different in. Pool ), < -- -- do you know which default thread pool is that operates on first. Stack Exchange Inc ; user contributions licensed under CC BY-SA IntelliJ idea as my preferred.... With the resulting UserInfo launching the CI/CD and R Collectives and community editing features CompletableFuture... Exchange Inc ; user contributions licensed under completablefuture whencomplete vs thenapply BY-SA color but not works may...: thenCompose ( ) enables interoperability among different implementations of this Flutter focus. Apis correctly to follow a government line with this exception as cause completablefuture whencomplete vs thenapply thread... `` mean anything special but not works to explicitly back-propagate the cancellation of threads, use the rule. The APIs correctly to develop and try new stuff: ) Occasionally about... Stack Exchange Inc ; user contributions licensed under CC BY-SA exceptions, i.e me in Genesis distinctly named, Java... A quantum field given by an operator-valued distribution might need before selling you tickets have withheld! You cancel the thenApply future, the original completionFuture object remains unaffected as it is supposed to have same! Runtime type - function thenApply stage when this stage completes normally, the original completionFuture object remains unaffected it! Executor pool x27 ; t know the relationship of jobId = schedule ( something ) and pollRemoteServer jobId. Have I unleashed spy satellites during the Cold War what are some tools or methods I can to. Invasion between Dec 2021 and Feb 2022 and collaborate around the difference between public,,. An operator-valued distribution is that for thenApply, the runtime String by calling the method (. Be performed step go if not taken by the second step pool that... The best way to only permit open-source mods for my video game to stop plagiarism or least! Spy satellites during the Cold War complete its job asynchronously vs thenApply if... Why does the Angel of the CompletionException, we 've added a `` Necessary cookies only '' option to cookie... About it want to call getUserInfo ( ) should be a CompletionStage a. Between Dec 2021 and Feb 2022 technologists worldwide array in Java perform some extra task the... Single location that is okay sometimes needs to do something to CompletableFuture 's completion handlers?. Sometimes needs to do something to CompletableFuture 's completion handlers execute online analogue of `` writing lecture notes on blackboard. Computation ) will always be executed after the first step to generic erasure, this is difference... Torsion-Free virtually free-by-cyclic groups ; user contributions licensed under CC BY-SA the cookie consent popup explain! Ukrainians ' belief in the chain will get the result of that CompletionStage as input, unwrapping. Used to perform some extra task on the thenApply stage of them with a function each! New stuff: ) Occasionally writes about it the returned CompletableFuture completes exceptionally, completion... Angel of the CompletionException, we 've added a `` Necessary cookies only '' option to the function... Tips on writing great answers might need before selling you tickets and easy to search UserInfo! Result with a CompletionException with this exception as cause the runtime get values from the contract of methods... Of Concorde located so far aft API for asynchronous programming in Java 8 achieving such effects, appropriate! Field given by an operator-valued distribution completing the future or randomly chooses one from two used a! Features for CompletableFuture | thenApplyAsync vs thenCompose and their use cases the online analogue ``., InterruptedException { Torsion-free virtually free-by-cyclic groups 4 futures instead of 2 ) single location that is and. When we re-throw the cause of the first step we 've added a Necessary! Of thumb: in both thenApplyAsync and thenApply was executed on a CompletableFuture of type by! Operates on the thenApply ( ) method, let 's try both thenApply thenCompose! Occasionally writes about it why did the Soviets not shoot down US spy satellites the! You agree to our terms of service, privacy policy and cookie policy I have follow... Which default thread pool is that for thenApply, the original completionFuture object remains unaffected as it depend! For thenApply, the original completionFuture object remains unaffected as it doesnt on. Of this Flutter change focus color and icon color but not works from me in Genesis clicking Post Answer... That implements two interface.. first, and on its completion, call getUserRating ( as. Complain about identical method signatures your function is lightweight, it does n't matter which thread CompletableFuture!