Collections, for example. Functional reactive programming. Things like I write in Java now: https://github.com/JetBrains/jetpad-mapper https://github.com/JetBra

Collections, for example. Functional reactive programming. Things like I write in Java now: https://github.com/JetBrains/jetpad-mapper https://github.com/JetBrains/jetpad-mapper I remember when Java started to have generics in 1.5. It was very hard to go back to 1.4 after having used that. I feel that I just can't program without them any longer.