Overview of the Reactive Program:

RXJAVA is a framework for response programming in the Java library.It provides a set of rich tools and models that enable developers to handle asynchronous and event flows in a more concise, reliable and maintainable way. Response programming is a programming paradigm based on data flow and changing communication.It enables highly decoupling and flexibility by disassembling the application into an independent component. These components are communicated and interactive through the event flow. In RXJAVA, there are three core concepts: Observer, Observable, and Subscripting. Observer is an interface that indicates the event consumer, which defines a set of methods for handling events.Observer can subscribe to an observed object to receive events issued by the object. Observed object is an interface for representative events, which can issue a series of events.Observed objects can be subscribed by observers. Once the incident occurs, all observers will be notified. Subscription is a connection between observer and observed objects.Through subscriptions, observer can receive events issued by observed objects.Subscription can also be used to control the flow rate and cancel subscription. Rxjava builds a powerful response programming model by combining these three concepts.It provides rich operators for processing and conversion event flows, filtering and combined events, mergers and split events, and so on. Below is a simple Java code example, which shows how to use RXJAVA observer mode: import io.reactivex.rxjava3.core.Observable; import io.reactivex.rxjava3.core.Observer; import io.reactivex.rxjava3.disposables.Disposable; public class RxJavaExample { public static void main(String[] args) { Observable<String> observable = Observable.just("Hello, RxJava!"); Observer<String> observer = new Observer<String>() { @Override public void onSubscribe(Disposable d) { System.out.println("Subscribed"); } @Override public void onNext(String s) { System.out.println(s); } @Override public void onError(Throwable e) { System.err.println("Error: " + e.getMessage()); } @Override public void onComplete() { System.out.println("Completed"); } }; observable.subscribe(observer); } } In this example, we first created an observed object `Observable`, which issued a string event.Then, we created an observer `Observer`, which defines the logic of the incident.Finally, we subscribe to the observer through the `Subscripe` method with observed objects, thereby establishing the relationship between them. When running this code, we can see that the output result is: Subscribed Hello, RxJava! Completed This shows that the observer successfully subscribed to observed objects and received the incident. In summary, RXJAVA is a powerful response programming framework. It provides a simple, reliable and maintainable way to deal with asynchronous and event flow through the relationship between observer mode, observable objects and subscriptions.EssenceBy using RXJAVA's operating symbols and modes reasonably, developers can more efficiently handle complex asynchronous operation and event processing logic.