Execute multiple queries in parallel via Streams

Question

I am having the following method:

public String getResult() {

        List serversList = getServerListFromDB();

        List ap         


        

Answer 1

You may utilize CompletableFuture this way:

public String getResult() {

    // Create Stream of tasks:
    Stream>> tasks = Stream.of(
            () -> getServerListFromDB(),
            () -> getAppListFromDB(),
            () -> getUserFromDB());

    List> lists = tasks
         // Supply all the tasks for execution and collect CompletableFutures
         .map(CompletableFuture::supplyAsync).collect(Collectors.toList())
         // Join all the CompletableFutures to gather the results
         .stream()
         .map(CompletableFuture::join).collect(Collectors.toList());

    // Use the results. They are guaranteed to be ordered in the same way as the tasks
    return getResult(lists.get(0), lists.get(1), lists.get(2));
}