Java 8 Completable Futures allOf different data types

Question

I have 3 CompletableFutures all 3 returning different data types.

I am looking to create a result object that is a composition of the result returned by all the 3 fu

Answer 1

I was going down a similar route to what @Holger was doing in his answer, but wrapping the Service Calls in an Optional, which leads to cleaner code in the thenApplyAsync stage

CompletableFuture> classAFuture
    = CompletableFuture.supplyAsync(() -> Optional.ofNullable(service.getClassA())));

CompletableFuture> classBFuture
    = CompletableFuture.supplyAsync(() -> Optional.ofNullable(service.getClassB()));

CompletableFuture> classCFuture
    = CompletableFuture.supplyAsync(() -> Optional.ofNullable(service.getClassC()));

return CompletableFuture.allOf(classAFuture, classBFuture, classCFuture)
     .thenApplyAsync(dummy -> {
        ClassD resultClass = new ClassD();

        classAFuture.join().ifPresent(resultClass::setClassA)
        classBFuture.join().ifPresent(resultClass::setClassB)
        classCFuture.join().ifPresent(resultClass::setClassC)

        return resultClass;
     });