Next, we will cover various common operators that transform emissions. A series of operators in an Observable chain is a stream of transformations. You have already seen map(), which is the most obvious operator in this category. We will start with that one.
For a given Observable<T>, the map() operator will transform a T emission into an R emission using the provided Function<T,R> lambda. We have already used this operator many times, turning strings into lengths. Here is a new example: we can take raw date strings and use the map() operator to turn each one into a LocalDate emission, as shown in the following code snippet:
import io.reactivex.Observable;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
public class Launcher {
public static void main(String[] args) {
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("M/d
/yyyy");
Observable.just("1/3/2016", "5/9/2016", "10/12/2016")
...