MappingExamples.java

package com.packtpub.reactive.chapter04;

import static com.packtpub.reactive.common.Helpers.subscribePrint;

import java.nio.file.Paths;
import java.util.Arrays;
import java.util.concurrent.TimeUnit;

import rx.Observable;
import rx.Subscription;
import rx.functions.Func0;
import rx.functions.Func1;

import com.packtpub.reactive.common.CreateObservable;
import com.packtpub.reactive.common.Program;

/**
 * Demonstration of using map, flatMap, flatMapIterable and switchMap.
 * 
 * @author meddle
 */
public class MappingExamples implements Program {

	@Override
	public String name() {
		return "Examples of using Observable transformations";
	}

	@Override
	public int chapter() {
		return 4;
	}

	@Override
	public void run() {
		Observable<String> mapped = Observable.just(2, 3, 5, 8).map(v -> v * 3)
				.map(v -> (v % 2 == 0) ? "even" : "odd");

		subscribePrint(mapped, "map");

		System.out.println("-----------------");

		Observable<Integer> flatMapped = Observable.just(3, 5, 8).flatMap(
				v -> Observable.range(v, v));

		subscribePrint(flatMapped, "flatMap");

		System.out.println("-----------------");

		flatMapped = Observable
				.<Integer>just(-1, 0, 1)
				.map(v -> 2 / v)
				.flatMap(
						new Func1<Integer, Observable<Integer>>() {
							@Override
							public Observable<Integer> call(Integer v) {
								return Observable.<Integer>just(v);
							}
						},
						new Func1<Throwable, Observable<Integer>>() {
							@Override
							public Observable<Integer> call(Throwable e) {
								return Observable.just(0);
							}
						},
						new Func0<Observable<Integer>>() {
							@Override
							public Observable<Integer> call() {
								return Observable.just(42);
							}
						}
						);

		subscribePrint(flatMapped, "flatMap");
		System.out.println("-----------------");

		flatMapped = Observable.just(5, 432).flatMap(v -> Observable.range(v, 2),
				(x, y) -> x + y);

		subscribePrint(flatMapped, "flatMap");
		System.out.println("-----------------");
		
		Observable<String> fsObs = CreateObservable.listFolder(
				Paths.get("src", "main", "resources"),
				"{lorem.txt,letters.txt}")
				.flatMap(path -> CreateObservable.from(path), (path, line) -> path.getFileName() + " : " + line);

		subscribePrint(fsObs, "FS");

		Observable<?> fMapped = Observable.just(Arrays.asList(2, 4),
				Arrays.asList("two", "four"), Arrays.asList('t', 'f'),
				Arrays.asList(true, false)).flatMap(l -> Observable.from(l));

		subscribePrint(fMapped, "flatMap");
		Observable<?> fIterableMapped = Observable.just(Arrays.asList(2, 4),
				Arrays.asList("two", "four"), Arrays.asList('t', 'f'),
				Arrays.asList(true, false)).flatMapIterable(l -> l);

		subscribePrint(fIterableMapped, "flatMapIterable");
		System.out.println("-----------------");

		Observable<Object> obs = Observable
				.interval(40L, TimeUnit.MILLISECONDS).switchMap(
						v -> Observable.timer(0L, 10L, TimeUnit.MILLISECONDS)
								.map(u -> "Observable <" + (v + 1) + "> : " + (v + u)));

		Subscription sub = subscribePrint(obs, "switchMap");

		try {
			Thread.sleep(400L);
		} catch (InterruptedException e) {
		}
		sub.unsubscribe();

		System.out.println("-----------------");
	}

	public static void main(String[] args) {
		new MappingExamples().run();
	}
}