Multiple Null checks handling in java8

Question

Instead of multiple null checks in below case, I am planning to add something readable code instead. May be with the help of java 8 streams/maps. Can somebody help me with this

private String getRailsServiceClass(IRailsComponent railsComponent) {
        String serviceClass = "";
        if (railsComponent != null && railsComponent.getRailOffer() != null && railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct() != null && railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct().getFareBreakdownList() != null &&
                railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct().getFareBreakdownList().get(0).getPassengerFareList() != null && railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct().getFareBreakdownList().get(0).getPassengerFareList().get(0).getPassengerSegmentFareList() != null &&
                railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct().getFareBreakdownList().get(0).getPassengerFareList().get(0).getPassengerSegmentFareList().get(0).getCarrierServiceClassDisplayName() != null) {
            return railsComponent.getRailOffer().getRailProducts().get(0).getRailProduct().getFareBreakdownList().get(0).getPassengerFareList().get(0).getPassengerSegmentFareList().get(0).getCarrierServiceClassDisplayName();
        }
        return serviceClass;
    }

Answer 1

You can use Optional for your purpose.

String serviceClass = Optional.ofNullable(railsComponent)
           .map(IRailsComponent::getRailOffer)
           .map(RailOffer::getRailProducts)
           ...
           .orElse("");

Answer 2

Your code is bad because on each check you had to get the items in the lists again and again. That's a lot of I/O to do.

Without using any API (so pre-Java 8 solution) You can clean you code by checking each item one after all (depends on the accessiblity of each class but here is a fully developped condition

RailComponent rc = getRailComponent();
    if (rc != null) {
        RailOffer ro = rc.getRailOffer()
        if (ro != null) {
            RailProduct rp = ro.getRailProducts().get(0).getRailProduct();
            if (rp != null) {
                List<FareBreakDown> fbList = rp.getFareBreakdownList();
                if (fbList != null) {
                    List<PassengerFare> pfList = fb.get(0).getPassengerFareList();
                    if (pfList != null) {
                        List<PassengerSegmentFare> psfList = pfList.get(0).getPassengerSegmentFareList();
                        if (psfList != null) {
                            String carrierServiceClassDisplayName = psfList.get(0).getCarrierServiceClassDisplayName();
                            if (carrierServiceClassDisplayName != null) {
                                return carrierServiceClassDisplayName;
                            }
                        }
                    }
                }
            }
        }
    }

You see that's not THAT much of check once you reduce the verbosity of your code