test to show the difference between RxJava operators (concat , concatEager, merge)

RxJavaTest.java

import org.junit.Test;
import java.util.concurrent.TimeUnit;

import rx.Observable;
import rx.observers.TestSubscriber;

public class RxJavaTest{
    @Test
    public void testConcatenating(){
        Observable<String> first = Observable.just("first").delay(1,TimeUnit.SECONDS);
        Observable<String> second = Observable.just("second").delay(3,TimeUnit.SECONDS);
        Observable<String> third = Observable.just("third").delay(2,TimeUnit.SECONDS);

        TestSubscriber<String> subscriber=new TestSubscriber<>();
        final long[] startTime = {0};
        System.out.println("======= concat =======");
        Observable.concat(first, second, third)
                .doOnSubscribe(() -> startTime[0] += System.currentTimeMillis())
                .doOnNext(s -> System.out.println(s+" take "+(System.currentTimeMillis()-startTime[0])/1000 +" seconds"))
                .subscribe(subscriber);
        subscriber.awaitTerminalEvent();

        TestSubscriber<String> subscriber2=new TestSubscriber<>();
        final long[] startTime2 = {0};
        System.out.println("======= concatEager =======");
        Observable.concatEager(first, second, third)
                .doOnSubscribe(() -> startTime2[0] += System.currentTimeMillis())
                .doOnNext(s -> System.out.println(s+" take "+(System.currentTimeMillis()-startTime2[0])/1000 +" seconds"))
                .subscribe(subscriber2);
        subscriber2.awaitTerminalEvent();

        TestSubscriber<String> subscriber3=new TestSubscriber<>();
        final long[] startTime3 = {0};
        System.out.println("======= merge =======");
        Observable.merge(first, second, third)
                .doOnSubscribe(() -> startTime3[0] += System.currentTimeMillis())
                .doOnNext(s -> System.out.println(s+" take "+(System.currentTimeMillis()- startTime3[0])/1000 +" seconds"))
                .subscribe(subscriber3);
        subscriber3.awaitTerminalEvent();
    }
}