Скачать или смотреть Tutoriel JAVA8 N°14: Collectors 1 averagingInt, averagingLong, averagingDouble .

Java 8 How to use collectors averagingInt, averagingInt, averagingDouble with examples

This tutorial explains how to use the predefined averaging collectors returned by Collectors.averagingInt(), Collectors.averagingLong() and Collectors.averagingDouble() methods with examples. It first explains the method definitions of these 3 methods and then shows averaging collectors’ usage using Java 8 code example, along with detailed explanation of the code.

Definition of averaging collectors
All 3 averaging collectors have very similar signatures which are as follows –
Where,
– input for all 3 collectors is a Function which extracts an int/long/double type of value as it works on the objects of the stream.The definitions in fact use the predefined ToIntFunction/ ToLongFunction/ ToDoubleFunction which I will explain in the next section.
– output is a Collector with finisher(return type) of type Double.

How the averaging collector works
Given a stream of objects, averaging collectors provided by the methods Collectors.averagingInt(), Collectors.averagingLong() and Collectors.averagingDouble() reduce these objects to an average of their numerical value/numerical value equivalent.