How to check if object and nested fields are null [duplicate]

Answer 1

You could implement an interface on all objects with method that returns all child objects and create a method that calls itself recursively to verify that all objects are set.

Answer 2

Let assume that this is a check to prevent misuse of a method, so this should not occurs too many time.

Simply catch this exception, this will invalidate the value.

private boolean isValid(YourObject object){
    try{
         return object.A.B.C.D != null;
    } catch (NullPointerException npe){
        return false;
    }
}

Of course, don't use this solution if you are doing a lot of validation and those return false to often, exception are an heavy process.

EDIT :

As Fildor point it out, there is a cost to use a try-catch even without exception. But using this answer I can assume this will be limited and there is not much optimization to do on this unique line.

Answer 3

Optional is a good way in Java 8.

String value = foo.getBar().getBaz().toString();

With optional it will be:

String value = Optional.ofNullable(foo)
                       .map(Foo::getBar)
                       .map(Bar::getBaz)
                       .map(Baz::toString)
                       .orElse("EmptyString");