Hands-On Reactive Programming in Spring 5

Reducing stream elements

Project Reactor makes it possible to count() the number of elements in the stream, or check that all elements have required properties with Flux.all(Predicate). It is also easy to check whether at least one element has a desired property with the Flux.any(Predicate) operator.

We can check whether a stream has any elements with the hasElements operator or whether the stream contains the desired element with the hasElement operator. The latter implements the short-circuit logic and completes with true as soon as an element matches the value. Also, the any operator allows the checking of not only an elements' equality but also any other property by providing a custom Predicate instance. Let's check that a sequence has ...