Java JComboBox选择索引

Question

我有这部分代码：

String[] emailList = { "Choose an email type", "yahoo.com", "gmail.com", "mail.com", "OTHER"};
JComboBox emailComboBox = new JComboBox (emailList);
registerPanel.add(emailComboBox);
emailComboBox.setBounds(350, 286, 173, 20);

当用户选择索引0或4（选择..和其他）来执行某些操作时，该怎么办。