В чём основная концепция использования RxJava?

package fs.rxtest;

import io.reactivex.Observable;
import io.reactivex.ObservableEmitter;
import io.reactivex.ObservableOnSubscribe;
import io.reactivex.disposables.Disposable;
import io.reactivex.functions.Cancellable;

public class Main {
    public interface Listener{
        void onNewBoolean(Boolean bool);
    }

    Listener listener;

    void registeredListener(Listener listener){
        System.out.println("register");
        this.listener = listener;
    }
    void unregisteredListener(){
        System.out.println("unregister");
        this.listener = null;
    }


    public static void main(String[] args) {
        Main main = new Main();

        Observable<Boolean> booleanObservable = Observable.create(
                new ObservableOnSubscribe<Boolean>() {
                    @Override
                    public void subscribe(ObservableEmitter<Boolean> e) throws Exception {
                        main.registeredListener(new Listener() {
                            @Override
                            public void onNewBoolean(Boolean bool) {
                                if(!e.isDisposed()) {
                                    e.onNext(bool);
                                }
                            }
                        });
                        e.setCancellable(new Cancellable() {
                            @Override
                            public void cancel() throws Exception {
                                main.unregisteredListener();
                            }
                        });

                    }
                }
        );



        Disposable subscribe = booleanObservable.subscribe(System.out::println);
        main.setValue(true);
        main.setValue(true);
        main.setValue(true);
        main.setValue(true);
        subscribe.dispose();
        main.setValue(true);
        Disposable subscribe1 = booleanObservable.subscribe(b -> System.out.println("2:"));
        main.setValue(false);


    }

    private void setValue(boolean b) {
        if (listener!=null)
        listener.onNewBoolean(b);
    }
}