Replacing repetitive get statement with Java 8 Optional

Question

I have a use case, where I have nested classes and an object of the top class. I want to get a value which is at the Nth level. I\'m using getters repetitively to achieve th

Answer 1

Use Optional with a series of map() calls for a nice one-liner:

String getAValue(D d) {
   return Optional.ofNullable(d)
       .map(D::getC).map(C::getB).map(B::getA).map(A::getA1).orElse(null);
}

If anything is null along the chain, including d itself, the orElse() will execute.

Answer 2

Wrap each nested class in an Optional:

Class A {
    String a1;
}
Class B {
    Optional<A> a;
}
Class C {
    Optional<B> b;
}
Class D {
    Optional<C> c;
}

Then use flatMap and map to operate on these optional values:

String a1 = d.flatMap(D::getC) // flatMap operates on Optional
             .flatMap(C::getB) // flatMap also returns an Optional
             .flatMap(B::getA) // that's why you can keep calling .flatMap()
             .map(A::getA1)    // unwrap the value of a1, if any
             .orElse("Something went wrong.") // in case anything fails

You might want to check out the concept of Monads. And if you're feeling adventurous, Scala is too distant from Java.