Hi Jerbo,
Thank you for taking time to analyze all this code. I appreciate a lot.
You cannot create an object of class with an empty constructor, if the constructor of that class has parameters. We already asked the professor about this and he said think about it. Finally, someone told me that since class Record is a utility for the InventorySet class then I should do the following:
The variable "m" contains a record object then i would need to cast it to a record, and then check its checkout values. I have already done the first part.

Then here is the changes to the method and it is working now:
public void checkOut(VideoObj video) {
// TODO
Object m = _data.get(video);
Record c = (Record)m;
if(m == null || c.numout < 0 )
{throw new IllegalArgumentException();
_data.remove(video);
}
}
Have a good day Jerbo and one again thanks a lot.
Dounia