Collector

Last week, I described a use-case for a custom Stream Collector. I received a intriguing comment on Twitter: There was a 'Not Found' error fetching URL: 'https://twitter.com/Miguucm/status/1389258245886390292' Hats off to you, Miguel! Your comment revealed a method I didn’t know! So I decided to investigate what the teeing() method is about. Returns a Collector that is a composite of two downstream collectors. Every element passed to the resulting collector is processed by both down

Java Stream’s Collectors methods fit most use-cases. They allow returning either a Collection or a scalar. For the former, you use one of the toXXX() method, for the latter, one of the reducing() one. Let’s imagine an e-commerce platform that implements a shopping cart. The cart is modeled as the following: This diagram might translate into the following (abridged) code: Product.java public class Product { private final Long id; (1) priva