Learning RxJava - Second Edition

startWithItem()

For a given Observable<T>, the startWithItem() operator (previously called startWith() in RxJava 2.x) allows you to insert a value of type T that will be emitted before all the other values. For instance, if we have an Observable<String> that emits drink names we would like to print, we can use startWithItem() to insert a header as the first value of the stream:

import io.reactivex.rxjava3.core.Observable;public class Ch3_15 {    public static void main(String[] args) {        Observable<String> menu =               Observable.just("Coffee", "Tea", "Espresso", "Latte");       //print menu        menu.startWithItem("COFFEE SHOP MENU")            .subscribe(System.out::println);    }}

The output of the preceding code snippet is as follows:

COFFEE SHOP MENUCoffeeTeaEspresso ...