Interesting attempt, however: 1. There was no need to implement Set interface to support foreach loop. Iterable would be sufficient. Set is too specific and is

Interesting attempt, however: 1. There was no need to implement Set interface to support foreach loop. Iterable would be sufficient. Set is too specific and is not an obvious choice (for return type interoperability in subclasses sometimes it would be more convenient to have List). 2. Moving from isPresent/get to try/catch checked exception will produce worse result. Either you wrap ‘get’ immediately and get more verbose code, or you catch somewhere else and loose the context and readability. In “throws Exception” methods absence of stack trace will be painful. 3. Renaming ‘map’ to ‘then’ is too late. “Then” was used in functional style libraries more than 15 years ago, Java 8 settled the naming convention and it’s better to follow it. 4. What Optional is often missing is the context of empty state. It would be cool to have an implementation of None with a Throwable cause (and orElseThrow throwing it wrapped).