reactor-core/src/main/java/reactor/core/publisher/FluxConcatArray.java
FluxConcatArray<T> concatAdditionalSourceLast(Publisher<? extends T> source) {
		int n = array.length;
		@SuppressWarnings("unchecked")
		Publisher<? extends T>[] newArray = new Publisher[n + 1];
		System.arraycopy(array, 0, newArray, 0, n);
		newArray[n] = source;
		
		return new FluxConcatArray<>(delayError, newArray);
	}
FluxConcatArray<T> concatAdditionalSourceLast(Publisher<? extends T> source) {
		int n = array.length;
		@SuppressWarnings("unchecked")
		Publisher<? extends T>[] newArray = new Publisher[n + 1];
		System.arraycopy(array, 0, newArray, 0, n);
		newArray[n] = source;
		
		return new FluxConcatArray<>(delayError, newArray);
	}
Returns a new instance which has the additional source to be merged together with
the current array of sources.
<p>
This operation doesn't change the current FluxMerge instance.

@param source the new source to merge with the others
@return the new FluxConcatArray instance