Is this what you are looking for? askPong(“cause error”) .handle( (pong, ex) -> ex == null ? CompletableFuture.completedFuture(pong) : askPong(“Ping”) ).thenCompose(x -> x); Also, do not use the …Async methods unless you intend for the body of the supplied function to be executed asynchronously. So when you do something like .handleAsync((x, t) -> { if … Read more
Unlike Java 9 and later, Java 8 does not provide a static factory method for this scenario. The default constructor can be used instead: CompletableFuture<T> future = new CompletableFuture<>(); future.completeExceptionally(exception);
I ran into something similar and came up with a solution that does not use reflection and seems to work well with JDK9-JDK11. Here is what the javadocs say: The parameters used to construct the common pool may be controlled by setting the following system properties: java.util.concurrent.ForkJoinPool.common.threadFactory – the class name of a ForkJoinPool.ForkJoinWorkerThreadFactory. The … Read more
As @nullpointer points out, the documentation tells you what you need to know. However, the relevant text is surprisingly vague, and some of the comments (and answers) posted here seem to rely on assumptions that aren’t supported by the documentation. Thus, I think it’s worthwhile to pick it apart. Specifically, we should read this paragraph … Read more
TL;DR: The ForkJoinPool uses daemon threads, whereas the ExecutorService is using non-daemon threads. The latter keep the JVM alive; the former do not. Also, the main thread is a non-daemon thread and when you block it waiting for the CompletableFuture to complete it remains alive (thus keeping the JVM alive). Daemon vs Non-Daemon Threads A … Read more
Use CompletableFuture.allOf(…): static<T> CompletableFuture<List<T>> sequence(List<CompletableFuture<T>> com) { return CompletableFuture.allOf(com.toArray(new CompletableFuture<?>[0])) .thenApply(v -> com.stream() .map(CompletableFuture::join) .collect(Collectors.toList()) ); } A few comments on your implementation: Your use of .thenComposeAsync, .thenApplyAsync and .thenCombineAsync is likely not doing what you expect. These …Async methods run the function supplied to them in a separate thread. So, in your case, you … Read more