public abstract <U, V> CompletionStage<V> thenCombineAsync (CompletionStage<? extends U> other, BiFunction<? super T, ? super U, ? extends V> fn)

Returns a new CompletionStage that, when this and the other given stage both complete normally, is executed using this stage's default asynchronous execution facility, with the two results as arguments to the supplied function. See the CompletionStage documentation for rules covering exceptional completion.

Parameters:
other    the other CompletionStage
fn    the function to use to compute the value of the returned CompletionStage
<U>    the type of the other CompletionStage's result
<V>    the function's return type

Returns:  the new CompletionStage