“Optional – the mother of all bikesheds”

Speaker: Stuart Marks
#OptionalBikeshed

The deck is available online

For more blog posts from JavaOne, see the table of contents

Showed early version of “optional” (stream returning null)

Review of basics

• Two states – present (contains non null reference) or absent
• Don’t say “null optional”. Say “absent” or “empty”
• Optionals are immutable
• equals() and hashCode() work as one would expect – useful for JUnit because can call assertEquals()

New in Java 9

• stream() – stream with 0 or 1 elements
• ifPresentOrElse(Consumer)
• or(Supplier)

Good code and Best practices

• Never set an Optional variable to null. It should be Optional.empty() as default.
• If method returns Optional, never return a null either.
• Intended for return types where might or might not have a value to return.
• Don’t call get() as could be empty optional
• Use isPresent() and get() as last resort
• Using .map().orElse() chained after stream pipeline gives fluent API calls
• Calling filter() returns original value only if non-empty optional that matches. else returns empty. Using filter() and orElseThrow() is good for validation
• [and more see the deck]

My take: Amazed there is so much to say about Optional! Excellent set of best practices. And excellent point on not calling an optional “null.” I needed to leave early as my session is immediately after this one. And I really wanted to know “what’s with the bikeshed” which is covered last.  It’s a nice collection of quotes. So I found the deck and best practices online. There’s also a youtube video linked so you can watch at home.