src/main/java/io/reactivex/Observable.java
@SuppressWarnings({ "unchecked", "rawtypes" })
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Observable<T> concat(Iterable<? extends ObservableSource<? extends T>> sources) {
        ObjectHelper.requireNonNull(sources, "sources is null");
        return fromIterable(sources).concatMapDelayError((Function)Functions.identity(), bufferSize(), false);
    }
@SuppressWarnings({ "unchecked", "rawtypes" })
    @CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public static <T> Observable<T> concat(Iterable<? extends ObservableSource<? extends T>> sources) {
        ObjectHelper.requireNonNull(sources, "sources is null");
        return fromIterable(sources).concatMapDelayError((Function)Functions.identity(), bufferSize(), false);
    }
@ SuppressWarnings ( { "unchecked" , "rawtypes" } ) @ CheckReturnValue @ NonNull @ SchedulerSupport ( SchedulerSupport . NONE ) public static < T > Observable < T > concat ( Iterable < ? extends ObservableSource < ? extends T > > sources ) { ObjectHelper . requireNonNull ( sources , "sources is null" ) ; return fromIterable ( sources ) . concatMapDelayError ( ( Function ) Functions . identity ( ) , bufferSize ( ) , false ) ; }
Concatenates elements of each ObservableSource provided via an Iterable sequence into a single sequence
of elements without interleaving them.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/concat.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code concat} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@param <T> the common value type of the sources
@param sources the Iterable sequence of ObservableSources
@return the new Observable instance
Concatenates elements of each ObservableSource provided via an Iterable sequence into a single sequence of elements without interleaving them . <p > <img width = 640 height = 380 src = https : // raw . github . com / wiki / ReactiveX / RxJava / images / rx - operators / concat . png alt = > <dl > <dt > <b > Scheduler : < / b > < / dt > <dd > {