final JComboBox combo = new JComboBox();
panel.add(combo, BorderLayout.SOUTH);
combo.addItem("Double_Value");
combo.addItem("energy");
combo.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
TangoKey key = new TangoKey();
TangoKeyTool.registerWriteAttribute(key, "katy/gs/publisher", combo.getSelectedItem().toString());