Whats the most elegant way to add two numbers that are Optional

Question

I need to perform an add operation on two big decimals that are wrapped optionals:

Optional ordersTotal;
Optional newOrder;
<         


        

Answer 1

Note that your solution

ordersTotal=ordersTotal.flatMap(b -> Optional.of(b.add(newOrder.orElse(BigDecimal.ZERO))));

will produce an empty Optional, if ordersTotal is empty, even if newOrder is not.

This could be fixed by changing it to

ordersTotal=ordersTotal
    .map(b -> Optional.of(b.add(newOrder.orElse(BigDecimal.ZERO))))
    .orElse(newOrder);

but I’d prefer

ordersTotal=ordersTotal
    .map(b -> newOrder.map(b::add).orElse(b))
    .map(Optional::of).orElse(newOrder);