Your question and your title seems contradictory to me. In your title it seems you want multiple comboboxes and 1 ItemListener. But your question starts with "I have two combo boxs, I want to add a separate itemListener to each one"
Nonetheless both are possible. And if you want to identify the calling combobox, you have to choices:
1/ call getItem() on the ItemEvent instance of the itemStateChanged() method (a cast will be required)
2/ make a custom ComboItemListener class (which of course implements ItemListener and performs your business logic) and just pass a ComboBox to its constructor as an argument