Run a List<CompletableFuture> One After Another

Question

So I have an interface SetupTask that has only a single method run() which returns a CompletableFuture . I have a List<SetupTask> . I want to run the first one and when that is complete run the second and when that is complete run the third and so on. Originally I tried CompletableFuture.allOf() but that would run them all in parallel.

Answer 1

You could chain all these tasks one after another consistently calling .thenCompose . This method executes some function that returns a CompletableFuture when the given stage is complete. I used CompletableFuture<Void> just to demonstrate how it would look like.

CompletableFuture<Void> current = CompletableFuture.completedFuture(null);
for (SetupTask task : tasks) {
    current = current.thenCompose(v -> task.run());
}