How to check if JSON object is empty in Java?

Question

In Java, if I use the following JSON string as an example, how would I check if the objects are empty/null?

{"null_object_1" : [], "null_object_2" : [null] }

I have tried using:

if(!jsonSource.isNull("null_object_1"))  {/*null_object_1 is not empty/null*/}
if(!jsonSource.isNull("null_object_2"))  {/*null_object_2 is not empty/null*/}

But these IF statements still return true (as if they are not empty/null).

Does anyone have a solution?

Edit: By "object", I actually meant array.