Hats off to you, Miguel! Your comment revealed a method I didn’t know!

So I decided to investigate what is the

teeing()method about

Returns a Collector that is a composite of two downstream collectors. Every element passed to the resulting collector is processed by both downstream collectors, then their results are merged using the specified merge function into the final result.

The resulting collector functions do the following:

* supplier: creates a result container that contains result containers obtained by calling each collector’s supplier

* accumulator: calls each collector’s accumulator with its result container and the input element

* combiner: calls each collector’s combiner with two result containers

* finisher: calls each collector’s finisher with its result container, then calls the supplied merger and returns its result.

_— _JavaDocs

We can indeed replace our custom

Collectorwith two simpleCollectorimplementations, one aggregating price rows and the other summing the cart’s price.

Let’s look at the final code and explain it line by line.

#java #api #stream #backend #learn-java-8 #beginners #teeing #java-8