ComboBox and simply Map

Hello, everyone.
How to view only keys in ComboBox?

        Map map = new HashMap();
        map.put("8px", FONT.font_size_8px);
        map.put("10px", FONT.font_size_10px);
        map.put("12px", FONT.font_size_12px);
        map.put("14px", FONT.font_size_14px);
        map.put("16px", FONT.font_size_16px);
        map.put("18px", FONT.font_size_18px);


ComboBox comboBoxSize = new ComboBox("SIZE",map.entrySet());

Try

comboBoxSize.setItemCaptionGenerator(Map.Entry::getKey);

Thanks!!!