Size of serialized object with null values

[jamesd128]

I want to create a serializable object with many different fields, but where, in any given object, only a few of those fields will have values. What I'm wondering is, when I write one of those objects to a file, will the file be a smaller size because only a few of the fields have values or will it be a bigger file to accommodate all the fields present on the object even if they are null?

[Sno]

I believe invisible space takes up bytes, so yes, pending on the amount of space you place between each field.

The only way to determine would be trial and error.