如何编辑JComboBox下拉箭头？

Question

How do you remove the background of a JComboBox dropdown arrow, leaving only the small triangle? The dropdown list was created using the JComboBox tool in Netbeans version 8.

Answer 1

@Drew I don't think the OP wants the button to disappear - he just wants the button to have no visible manifestation other than the arrow triangle:

JComboBox<String> box = new JComboBox<>();
final Color bg = box.getBackground();
box.setUI(new BasicComboBoxUI() {
    @Override
    protected JButton createArrowButton() {
        JButton b = super.createArrowButton();
        b.setBackground(bg);
        b.setBorderPainted(false);
        return b; 
   }
});