reactfx/src/main/java/org/reactfx/EventStreams.java
@SafeVarargs
    public static <T> EventStream<T> merge(EventStream<? extends T>... inputs) {
        return new EventStreamBase<T>() {
            @Override
            protected Subscription observeInputs() {
                return Subscription.multi(i -> i.subscribe(this::emit), inputs);
            }
        };
    }
@SafeVarargs
    public static <T> EventStream<T> merge(EventStream<? extends T>... inputs) {
        return new EventStreamBase<T>() {
            @Override
            protected Subscription observeInputs() {
                return Subscription.multi(i -> i.subscribe(this::emit), inputs);
            }
        };
    }
Returns an event stream that emits all the events emitted from any of
the {@code inputs}. The event type of the returned stream is the nearest
common super-type of all the {@code inputs}.

@see EventStream#or(EventStream)