Search for non empty list inside a list using Java 8 features

Question

I have a code fragment that I want to make more concise yet readable using Java 8 features like lambdas/streams etc.

Basically, there is a list of items and each item has a list of errors. If there is at least one item with at least one error, "failure" needs to be returned. If no items with any error, return "success".

Optional<List<Item>> optionalItemList = Optional.ofNullable(message.getItems());

if (optionalItemList.isPresent())
    for (Item item : optionalItemList.get()) {
        Optional<List<Error>> optionalErrorList = Optional.ofNullable((item.getErrors()));
        if(optionalErrorList.isPresent())
            if (!optionalErrorList.get().isEmpty()) {
                return "failure";
            }
        }
        return "success";

Answer 1

Optional is not meant to replace if statements, but to be used as a return value of methods. So I think you'd better not use it for this task. You can use the ternary operator along with Stream.allMatch instead:

return message.getItems() == null || 
       message.getItems().stream()
              .allMatch(i -> i.getErrors() == null || i.getErrors().isEmpty()) ?
      "success" :
      "failure";

On a side note, methods should never return null collections. The absence of elements should be expressed by returning empty collections. This would have made your code a lot easier:

return message.getItems().stream().allMatch(i -> i.getErrors().isEmpty()) ?
      "success" :
      "failure";