I wrote a method that in theory returns a TreeSet full of film titles. It was tested within its own calss and works. When I use the same method in my other class as you see at the bottom where set is TreeSet, I did the tests to print out the contents, and there is nothing. The variable method parameter comes from the main class and is a selection in a JComboBox.
Few questions, what's container defined as? Second, why do you use two iterators? If container is sorted this is ok, but if its not there's no guarentee the iterators are in the same ordering. For safety I tend to use one iterator and use the keySet() to retrieve the values such as:
As for your problem, there's not enough details to identify what is causing your results. Post more details.