Should databinding use weak or hard references?

Hard references prevent your objects from garbage collection.
Weak references are eligible for the garbage collector and therefore may return NULL value. Weak references are useful especially for large objects, that can be easily recreated.

This may shed some light on that topics...
what is hard reference in java?
Understanding Weak References
Weak References

I know what weak and hard references are. I am more interested in whether using weak or hard references is a better practice in a databinding implementation.

You mentioned about recreating the objects which the GC has collected away. Since the GC has already collected away the object, and the data binder has no more reference to the actual initial object, how can the application or the data binder still recreate the already-garbage-collected object with its last lost data?

For example, there is an object of Cat that has the property of Name. We have an instance of Cat with the name of "Kitty":

Cat myCat = new Cat();
myCat.Name = "Kitty";

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Suppose the data binder is referencing myCat via a weak reference, and myCat got garbage collected. The data binder wants to recreate the object as you said. The data binder could "new up" another instance of Cat, but it wouldn't know that the new Cat instance it creates need to have its Name property value as "Kitty", ie, the newly recreated object wouldn't be the same as the one it was garbage collected. In this case, wouldn't the newly recreated object be useless because it is a different thing and using it will lead to wrong data?

In that case, if you cannot easily recreate your object, you have to use a hard reference.

What I meant is following:
Supposed you have a treeview object that holds all files of a folder,  you can create that treeview when you need it and then release it. If the treeview is required later again, you can easily recreate it...