I think there is a valid approach to retrieving records based on a criteria
object that is of the same class as the object you are retrieving.

A Record object may be used as the criteria to find other Record objects.

If we have a method such as

Record[] find(Record record);

then the argument can have any of its fields as null
this would signify no filtering on that field.

A criteria object could be set up as so:

public Record(Integer key, String[] data);

new Record(null, new String {"Foo", "Bar", null, null, null, null, null})

I think Hibernate uses this approach.

But I'm a little unhappy about this, a null primary key?

Is this abuse of the object? should I have a separate criteria class?

I'm after the simplest design that I do feel happy about.