Optionals

Java Optionals For More Expressive Code

Java Optionals are Awesome

Optionals in Swift explained: 5 things you should know - SwiftLee

Optionals - a free Hacking with Swift tutorial

Optional Parameters in Java: A Deep Dive

Java 8 Optional isPresent(), OrElse() and get() Examples

Optionals in Swift. All about Optionals in Swift…, by Yasir

Swift Basics: Optionals

Optionals Swift by Sundell

Optionals in Swift

ios - Optional Double attributes in CoreData don't behave like optionals? - Stack Overflow

Java 8 Optional Class - GeeksforGeeks