Sometimes you may want to write the if-else control flow based on an Optional object.

For example, an API from a third party library declares Optional as its return type. You need to compose an if-else like control flow using that Optional object. Of course, it can be done by testing isPresent() in a traditional if-else statement.

var itemOpt = service.getItem(itemId);
if (itemOpt.isPresent()) {
} else {"missing item {}", itemId);

The above code doesn’t take any advantage of Optional. Actually, since Java 9 the ifPresentOrElse​(Consumer<? super T>, Runnable) method can be used to implement such control flow, which is a bit more elegant.

    item -> {
    () -> {"missing item {}", itemId);