Selgitage Project Reactor kasutamise kontseptsiooni ja põhiprintsiipe Java keeles.

Project Reactor is a library for reactive programming in Java, implementing the Reactive Streams specification. It allows creating asynchronous, non-blocking applications that efficiently utilize resources.

Core principles:

• Flux and Mono — main types: Flux represents a stream of 0..N elements, Mono — 0..1 element.
• Backpressure — control of data processing speed to prevent overwhelming the consumer.
• Operators — methods for transforming, filtering, and combining streams.
• Subscription — the reactive stream only starts working after subscription.

Example usage:

Flux.just(1, 2, 3, 4)
    .filter(i -> i % 2 == 0)
    .map(i -> i * 2)
    .subscribe(System.out::println); // Will print 4 and 8

In this way, Project Reactor helps to write scalable and responsive applications with convenient handling of asynchronous data streams.