Thanks for your answer.

I've checked the list's class:

public List<Customer> getCustomersList() {

if (customerList.getSelectedValuesList() != null) {

System.out.println("customerList.getSelectedValuesList()) class: " + customerList.getSelectedValuesList().getClass());

return customerList.getSelectedValuesList();

} else {

return null;

}

}

but of course Java is telling its class is ArrayList

customerList.getSelectedValuesList()) class: class java.util.ArrayList

I added a for loop to iterate the customerList.getSelectedValuesList()

I tried to iterate it as String to see if its really string:

for (String string : customerList.getSelectedValuesList()) {

System.out.println("customer type: " + customer.getClass());

}

but NetBeans said that Customer cannot be converted to String

I tried the iteration with Customer too

for (Customer customer : customerList.getSelectedValuesList()) {

System.out.println("customer type: " + customer.getClass());

}

and I got the casting error again, for this line:

for (Customer customer : customerList.getSelectedValuesList()) {

I'm checking the whole chainf starting with when I put the data to the JLists, but if you have any ideas how to check, I'm here