Converting future.get() to CompletionStage.whenComplete()?

Question

I currently have some code in Java which looks something like this, but I want to refactor this.

List<Object> combinedStatus = new ArrayList();
for (List<Long> batch: batches){
    CompletableFuture<Object> future = ask();
    futureHolder.add(future);
}

try {
   for (CompletableFuture<Object> future: futureHolder) { 
      response = future.get();
      combinedStatus.add(response.result());
   } catch (Exception e) {
       // log exception 
   }
return combinedStatus;

I see one major issue is that future.get() is blocking the thread. I want to refactor this to make it non blocking. Here is my refactored version - can someone give me some advice on if this is correct / makes sense / or how I can make this better?

for (List<Long> b: batches) {
   CompletionStage<Object> stage = ask();
    stage.whenComplete(
        (resp, ex) -> {
            if (ex != null) {
             // log exception 
           } else { 
               combinedStatus.add(response.result());
     });
}

returned combinedStatus;

Additionally, can someone explain to me what is the behavior of this if I call this in a loop