Is there a real reason to use Optional.of()?

Question

I\'ve read here why Optional.of() should be used over Optional.ofNullable(), but the answer didn\'t satisfy me at all, so I ask slightly different:

Answer 1

You are mixing up the API design rationale with knowledge within a particular implementation code. It’s perfectly possible that a method declares to return an Optional, because the value might be absent, while at a certain code location within the method, it is known to be definitely present. I.e.

String content;
public Optional firstMatch(String pattern) {
    Matcher m = Pattern.compile(pattern).matcher(content);
    return m.find()? Optional.of(m.group()): Optional.empty();
}

This method’s return type denotes a String that might be absent, while at the code locations creating an Optional instance, it is known whether the value is present or absent. It’s not about detecting a null value here.

Likewise, within the Stream API methods findFirst() and findAny(), it will be known at one point, whether there is a matching element, whereas supporting the conversion of its presence to absence in case of a matching null element is explicitly unsupported and supposed to raise a NullPointerException, per specification. Therefore, Optional.of will be used to return the matching element, which you can easily recognize in the stack trace when using Stream.of((Object)null) .findAny();