Swing/LoopComboBox のバックアップ(No.15)

Action up = new AbstractAction() {
  @Override public void actionPerformed(ActionEvent e) {
    JComboBox<?> c = (JComboBox<?>) e.getSource();
    int i = c.getSelectedIndex();
    c.setSelectedIndex(i == 0 ? c.getItemCount() - 1 : i - 1);
  }
};
Action down = new AbstractAction() {
  @Override public void actionPerformed(ActionEvent e) {
    JComboBox<?> c = (JComboBox<?>) e.getSource();
    int i = c.getSelectedIndex();
    c.setSelectedIndex(i == c.getItemCount() - 1 ? 0 : i + 1);
  }
};
ActionMap am = combo.getActionMap();
am.put("loopUp", up);
am.put("loopDown", down);
InputMap im = combo.getInputMap();
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_UP, 0), "loopUp");
im.put(KeyStroke.getKeyStroke(KeyEvent.VK_DOWN, 0), "loopDown");