src/main/java/io/reactivex/Observable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> serialize() {
        return RxJavaPlugins.onAssembly(new ObservableSerialized<T>(this));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Observable<T> serialize() {
        return RxJavaPlugins.onAssembly(new ObservableSerialized<T>(this));
    }
@ CheckReturnValue @ SchedulerSupport ( SchedulerSupport . NONE ) public final Observable < T > serialize ( ) { return RxJavaPlugins . onAssembly ( new ObservableSerialized < T > ( this ) ) ; }
Forces an ObservableSource's emissions and notifications to be serialized and for it to obey
<a href="http://reactivex.io/documentation/contract.html">the ObservableSource contract</a> in other ways.
<p>
It is possible for an ObservableSource to invoke its Observers' methods asynchronously, perhaps from
different threads. This could make such an ObservableSource poorly-behaved, in that it might try to invoke
{@code onComplete} or {@code onError} before one of its {@code onNext} invocations, or it might call
{@code onNext} from two different threads concurrently. You can force such an ObservableSource to be
well-behaved and sequential by applying the {@code serialize} method to it.
<p>
<img width="640" height="400" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/synchronize.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code serialize} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@return an {@link ObservableSource} that is guaranteed to be well-behaved and to make only serialized calls to
its observers
@see <a href="http://reactivex.io/documentation/operators/serialize.html">ReactiveX operators documentation: Serialize</a>
Forces an ObservableSource s emissions and notifications to be serialized and for it to obey <a href = http : // reactivex . io / documentation / contract . html > the ObservableSource contract< / a > in other ways . <p > It is possible for an ObservableSource to invoke its Observers methods asynchronously perhaps from different threads . This could make such an ObservableSource poorly - behaved in that it might try to invoke { @code onComplete } or { @code onError } before one of its { @code onNext } invocations or it might call { @code onNext } from two different threads concurrently . You can force such an ObservableSource to be well - behaved and sequential by applying the { @code serialize } method to it . <p > <img width = 640 height = 400 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / synchronize . png alt = > <dl > <dt > <b > Scheduler : < / b > < / dt > <dd > { @code serialize } does not operate by default on a particular { @link Scheduler } . < / dd > < / dl >