How to iterate over all the declared fields of an object of a class [duplicate]

This question already has an answer here:

• Is it possible in Java to check if objects fields are null and then add default value to all those attributes? 6 answers

There are many answers on stackoverflow about how to iterate through the declared fields of a class. Can I do this with an object? For example, say I want to iterate through all the fields of an object of MyClass after creation to check which fields are null (I know this is not practical). Is there any way to do this?