Returning a Value, or a Default, From a Java Optional

Java Optionals are great for giving you flexibility over interacting with values that may not be present, and include a means for more safely retrieving values from nullable types.

For instance, you may want to call a method on a maybe-null object passed into your method, or return a default value:

private static String getName(Principal nullable) {
  Optional<Principal> maybePrincipal = Optional.ofNullable(nullable);
  if (maybePrincipal.isPresent()) {
    return maybePrincipal.get().getName();
  } else {
    return "<unknown>";
  }
}

This is fine, but doesn't follow the functional style that's possible with the Optional class.

What you may want to do instead is the following (linebreaks added for visibility):

private static String getName(Principal nullable) {
  Optional<Principal> maybePrincipal = Optional.ofNullable(nullable);
  return maybePrincipal
    .map(Principal::getName)
    .orElse("<unknown>");
}