Check not null in Java

Question

Imagine I have, say, XML-generated entity in Java that holds some data I need. For example:

<Car>
   <Engine>
      <Power>
         175
      </Power>
   </Engine>
</Car>

So if I need an engine power, I, followed by the best practices of business software development, will do the next thing:

Car car = dao.getCar()
Power power = car != null && car.engine != null ? power : null
return power

I hate this. Sometimes it seems that half of the code is just null checks.

Any ideas?

Answer 1

Take a look at Java 8 Optional class. It does exactly that: it avoids the ugly checks on null.

In your case, you could use this snippet of code to avoid them:

Car car = dao.getCar();
Optional<Car> optionalCar = Optional.ofNullable(car); 
Optional<Power> optionalPower = getPowerIfPresent(optionalCar);

Power power = Optional.empty();
if(optionalPower.isPresent()) {
    power = optionalPower.get();
}

after writing a function that returns the power of a given car:

public static Optional<Power> getPowerIfPresent(Optional<Car> car) {
    return car
        .flatMap(c -> c.getEngine())
        .map(e -> e.getPower());
}