code: @SuppressWarnings("unchecked")
      @CheckReturnValue
      @BackpressureSupport(BackpressureKind.FULL)
      @SchedulerSupport(SchedulerSupport.NONE)
      public static <T> Flowable<T> just(T item1, T item2, T item3) {
          ObjectHelper.requireNonNull(item1, "The first item is null");
          ObjectHelper.requireNonNull(item2, "The second item is null");
          ObjectHelper.requireNonNull(item3, "The third item is null");
  
          return fromArray(item1, item2, item3);
      }
docs: Converts three items into a Publisher that emits those items.
  <p>
  <img width="640" height="315" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/just.m.png" alt="">
  <dl>
  <dt><b>Backpressure:</b></dt>
  <dd>The operator honors backpressure from downstream and signals each value on-demand (i.e., when requested).</dd>
  <dt><b>Scheduler:</b></dt>
  <dd>{@code just} does not operate by default on a particular {@link Scheduler}.</dd>
  </dl>
  
  @param item1
  first item
  @param item2
  second item
  @param item3
  third item
  @param <T>
  the type of these items
  @return a Flowable that emits each item
  @see <a href="http://reactivex.io/documentation/operators/just.html">ReactiveX operators documentation: Just</a>