How to check if all non-primitive elements in object is null

Question

Is there any shortcut for checking if an objects all elements(and also their elements) are null. For example I want to check If a country object(and its city and its street) is null or not? I don't want to check them one by one like;

country == null || country.city == null || country.city.street == null


public class Country{

  City city;
  ....

}

public class City{

  Street street;
  ....
}

public class Street{
  ....
}

No, there's no shortcut. It's your job to implement this logic. — JB Nizet, Mar 07 '14 at 09:32
May be you have to write your own method to check all and return true/false accordingly. — Jay, Mar 07 '14 at 09:32
@kocko No, a `String` which _is_ an `Object` - a non-primitive variable _can_ be `null`. — Hungry Blue Dev, Mar 07 '14 at 09:34
[Reflection](http://docs.oracle.com/javase/7/docs/api/java/lang/reflect/package-summary.html) — PeterMmm, Mar 07 '14 at 09:37
What you are facing is basically the thing why there's something as constructors - to ensure a set of assumptions on your data, e.g. that some fields are not null. If you don't want to enforce given fields through a constructor, you have to cope with this generic data container and check everything by hand. — Smutje, Mar 07 '14 at 09:39

score 1 · Accepted Answer · edited May 23 '17 at 11:49

1

There is no shortcut: you have to browse recursively your instances and check their fields. You could use a custom version of the browser shown in How to list all properties exposed by a Java class and its ancestors in Eclipse?. Anyway that approach would make sense if you are working with esoteric legacy code, whereas if you are writing new classes is better enforce all not-nulls in constructor of factory methods.

edited May 23 '17 at 11:49

Community

1
1

answered Mar 07 '14 at 10:41

robermann

1,722
10
19

You have to browse recursively? I'd think when you have to do that, the answer is already clear - not all contained references are null. – Ingo Mar 07 '14 at 11:56
they could be null on the second level, and so on :) – robermann Mar 07 '14 at 12:47
1

But then the object you started with must have had at least one non-null reference, and so the check can return false. – Ingo Mar 07 '14 at 12:55

How to check if all non-primitive elements in object is null

1 Answers1