Testing asyncronous observables to parallelize work

SampleTest.java

public class SampleTest {
    @Test
    public void testObservableParallel() {
        List<String> terminals = new ArrayList<>();

        for (int i = 0; i < 100000; i++) {
            terminals.add(i, String.format("Terminal %s", i + 1));
        }

        PublishSubject<String> publisher = PublishSubject.create();

        long start = System.currentTimeMillis();

        publisher.subscribe(id -> {
            System.out.print("Result: " + id);
            System.out.println("   Thread: " + Thread.currentThread());
        }, error -> {}, () -> {
            final long executionTime = System.currentTimeMillis() - start;
            System.out.println(String.format("Execution time: %s", executionTime));
        });

        Observable.from(terminals)
                .subscribe(terminalId ->
                                Observable.just(terminalId)
                                        .subscribeOn(Schedulers.computation())
                                        .subscribe(publisher::onNext), error -> {}, publisher::onCompleted);
    }

    @Test
    public void testObservableSerial() {
        List<String> terminals = new ArrayList<>();

        for (int i = 0; i < 100000; i++) {
            terminals.add(i, String.format("Terminal %s", i + 1));
        }

        long start = System.currentTimeMillis();

        Observable.from(terminals)
                .subscribe(terminalId -> {
                    System.out.print("Result: " + terminalId);
                    System.out.println("   Thread: " + Thread.currentThread());
                }, error -> {}, () -> {
                    final long executionTime = System.currentTimeMillis() - start;
                    System.out.println(String.format("Execution time: %s", executionTime));
                });
    }
}