How do I stop this pop up event from populating he jcombobox each time it is clicked?

See more:

Java

SQL

JDBC

Swing

Each time I click on the JCombobox's arrow to show the list of exercises, it will continue to populate the combo box with duplicates entries shown in the image, made code is also inserted. I know its to know with the re-clicking of the arrow due to the popupmenulistener, but unsure how to correct this if someone could help -

<pre>       
exerciseList.addPopupMenuListener(new PopupMenuListener() {
            @Override
            public void popupMenuWillBecomeVisible(PopupMenuEvent e) {
                ArrayList<String> nameList = new ArrayList<>(getComboValues());
                
                for (String name : nameList) {
                    exerciseList.addItem(name);
                }


            }

            @Override
            public void popupMenuWillBecomeInvisible(PopupMenuEvent e) {
            }
            @Override
            public void popupMenuCanceled(PopupMenuEvent e) {

            }
        });
    }

    public ArrayList<String> getComboValues () {

        ArrayList<String> exerciseNames = new ArrayList<>();

        try {
            Connection connection = SQLConnection.connection();
            Statement statement = connection.createStatement();
            String select = "SELECT ExerciseName FROM exercises ORDER BY ExerciseName ASC";
            ResultSet rs = statement.executeQuery(select);

            while (rs.next()) {

                exerciseNames.add(rs.getString("ExerciseName"));

            }
        } catch (SQLException ex) {
            throw new RuntimeException(ex);
        }
        return exerciseNames;
    }
}

What I have tried:

Tried using break within the for loop but it just shows one of the values from the database, understandably. But each time I click on the combobox, it continues to fill it with duplicates of the value after break was implemented.