reactor-core/src/main/java/reactor/core/publisher/Flux.java
public final Mono<T> elementAt(int index, T defaultValue) {
		return Mono.onAssembly(new MonoElementAt<>(this, index, defaultValue));
	}
public final Mono<T> elementAt(int index, T defaultValue) {
		return Mono.onAssembly(new MonoElementAt<>(this, index, defaultValue));
	}
Emit only the element at the given index position or fall back to a
default value if the sequence is shorter.

<p>
<img class="marble" src="doc-files/marbles/elementAtWithDefault.svg" alt="">

@reactor.discard This operator discards elements that appear before the requested index.

@param index zero-based index of the only item to emit
@param defaultValue a default value to emit if the sequence is shorter

@return a {@link Mono} of the item at the specified zero-based index or a default value