operation.setOperator(Operator.ADD);
UserListOperation[] operations = new UserListOperation[] {operation};
// Add user list.
UserListReturnValue result = adwordsUserListService.mutate(operations);
// Display results.
if (result != null && result.getValue() != null) {
// Capture the ID(s) of the conversion.
List<String> conversionIds = new ArrayList<String>();