How to asynchronously call a method in Java

Question

I ve been looking at Go s goroutines lately and thought it would be nice to have something similar in Java  As far as I ve searched the common way to parallelize a method call is to do something like   final String x    somethingelse   new Thread new Runnable                public void run                     x matches  something                          start      Thats not very elegant  Is there a better way of doing this  I needed such a solution in a project so I decided to implement my own wrapper class around a async method call   I published my wrapper class in J-Go  But I don t know if it is a good solution  The usage is simple   SampleClass obj       FutureResult lt Integer gt  res       Go go   new Go obj   go callLater res   intReturningMethod   10             10 is a Integer method parameter       Do something else       System out println  Result    res get                 Blocks until intReturningMethod returns   or less verbose   Go with obj  callLater  myRandomMethod          Go away if  Go lastResult   isReady                     Blocks until myRandomMethod has ended     System out println  Method is finished       Internally I m using a class that implements Runnable and do some Reflection work to get the correct method object and invoking it   I want some opinion about my tiny library and on the subject of making async method calls like this in Java  Is it safe  Is there already a simplier way

User · Answer

I just discovered that there is a cleaner way to do your

new Thread(new Runnable() {
    public void run() {
        //Do whatever
    }
}).start();

(At least in Java 8), you can use a lambda expression to shorten it to:

new Thread(() -> {
    //Do whatever
}).start();

As simple as making a function in JS!

User · Answer

You may wish to also consider the class java util concurrent FutureTask   If you are using Java 5 or later  FutureTask is a turnkey implementation of  A cancellable asynchronous computation    There are even richer asynchronous execution scheduling behaviors available in the java util concurrent package  for example  ScheduledExecutorService   but FutureTask may have all the functionality you require   I would even go so far as to say that it is no longer advisable to use the first code pattern you gave as an example ever since FutureTask became available    Assuming you are on Java 5 or later

User · Answer

You can use the Java8 syntax for CompletableFuture  this way you can perform additional async computations based on the result from calling an async function   for example    CompletableFuture supplyAsync this  findSomeData                        thenApply this   intReturningMethod                        thenAccept this  notify     More details can be found in this article

User · Answer

You can use Future-AsyncResult for this     Async public Future lt Page gt  findPage String page  throws InterruptedException       System out println  Looking up     page       Page results   restTemplate getForObject  http   graph facebook com     page  Page class       Thread sleep 1000L       return new AsyncResult lt Page gt  results       Reference  https   spring io guides gs async-method

User · Answer

Java 8 introduced CompletableFuture available in package java util concurrent CompletableFuture  can be used to make a asynch call    CompletableFuture runAsync    - gt           method call or code to be asynch

User · Answer

Java also provides a nice way of calling async methods  in java util concurrent we have ExecutorService that helps in doing the same  Initialize your object like this -   private ExecutorService asyncExecutor   Executors newFixedThreadPool Runtime getRuntime   availableProcessors       and then call the function like-  asyncExecutor execute    - gt                             TimeUnit SECONDS sleep 3L

User · Answer

There is also nice library for Async-Await created by EA  https   github com electronicarts ea-async  From their Readme   With EA Async  import static com ea async Async await  import static java util concurrent CompletableFuture completedFuture   public class Store       public CompletableFuture lt Boolean gt  buyItem String itemTypeId  int cost                if  await bank decrement cost                  return completedFuture false                     await inventory giveItem itemTypeId            return completedFuture true             Without EA Async  import static java util concurrent CompletableFuture completedFuture   public class Store       public CompletableFuture lt Boolean gt  buyItem String itemTypeId  int cost                return bank decrement cost               thenCompose result - gt                    if  result                        return completedFuture false                                     return inventory giveItem itemTypeId  thenApply res - gt  true

User · Answer

This is not really related but if I was to asynchronously call a method e g  matches    I would use   private final static ExecutorService service   Executors newFixedThreadPool 10   public static Future lt Boolean gt  matches final String x  final String y        return service submit new Callable lt Boolean gt                Override         public Boolean call   throws Exception               return x matches y                          Then to call the asynchronous method I would use   String x    somethingelse   try       System out println  Matches    matches x   something   get       catch  InterruptedException e        e printStackTrace      catch  ExecutionException e        e printStackTrace        I have tested this and it works  Just thought it may help others if they just came for the  asynchronous method

User · Answer

You can use  Async annotation from jcabi-aspects and AspectJ   public class Foo      Async   public void save            to be executed in the background         When you call save    a new thread starts and executes its body  Your main thread continues without waiting for the result of save

User · Answer

You can use AsyncFunc from Cactoos   boolean matches   new AsyncFunc    x - gt  x matches  something     apply  The text   get      It will be executed at the background and the result will be available in get   as a Future

User · Answer

i don t like the idea of using Reflection for that  Not only dangerous for missing it in some refactoring  but it can also be denied by SecurityManager   FutureTask is a good option as the other options from the java util concurrent package  My favorite for simple tasks         Executors newSingleThreadExecutor   submit task     little bit shorter than creating a Thread  task is a Callable or a Runnable

User · Answer

It s probably not a real solution  but now - in Java 8 - You can make this code look at least a little better using lambda expression   final String x    somethingelse   new Thread    - gt            x matches  something                         start      And You could even do this in one line  still having it pretty readable   new Thread    - gt  x matches  something    start

[java] How to asynchronously call a method in Java

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