sorting and ordering pk field in memory

[Zvonimir Spajic]

Hello,

is there a nice way to sort a List of Cayenne-Objects on o  
primary-key-field, e.g. "id" (pk) in memory, because the user can resort  
the existing list more than one time. I don't want to read it out from DB  
every time.
This doesn't help:
        this.resultList = new ArrayList(this.resultList);               
        Ordering ordering = new Ordering("id", true);
        ordering.orderList(this.resultList);
In this example the ordering is not correct or will not be changed.
Can anyone help with this...or have a better idea...

Thank you
Zvonimir