Java应用程序设计SwingGUIn（3）addItem(Object item);和insertItemAt(Object item,int index);JComboBox icb=new JComboBox();icb.addItem(“士兵证”);icb.addItem(“驾驶证”);icb.insertItemAt(“身份证”,0);NORTHWESTCENTEREASTSOUTHn焦点事件由FocusEvent类捕获，对于焦点事件可以通过实现FocusListener接口处理相应的事件；nFocusListener接口原型：public interface FocusListener extends EventListenerpublic void focusGained(FocusEvent e);public void focusLost(FocusEvent e);nFocusEvent类比较常用的方法getSource():获取触发事件的目标对象；例子：FocusEventDemo.javanMouseEvent类捕获鼠标事件，可通过MouseListener接口处理鼠标事件；nMouseListener有5个抽象方法（下页）BUTTON33标右键标右键
