选择组合框上的项目时执行 *** 作

这就是使用ActionLIstener的方法

import java.awt.FlowLayout;import java.awt.event.*;import javax.swing.*;public class MyWind extends Jframe{    public MyWind() {        initialize();    }    private void initialize() {        setSize(300, 300);        setLayout(new FlowLayout(FlowLayout.LEFT));        setDefaultCloseOperation(Jframe.EXIT_ON_CLOSE);        final JTextField field = new JTextField();        field.setSize(200, 50);        field.setText("   ");        JComboBox comboBox = new JComboBox();        comboBox.setEditable(true);        comboBox.addItem("item1");        comboBox.addItem("item2");        //        // Create an ActionListener for the JComboBox component.        //        comboBox.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent event) {     //     // Get the source of the component, which is our combo     // box.     //     JComboBox comboBox = (JComboBox) event.getSource();     Object selected = comboBox.getSelectedItem();     if(selected.toString().equals("item1"))     field.setText("30");     else if(selected.toString().equals("item2"))         field.setText("40"); }        });        getContentPane().add(comboBox);        getContentPane().add(field);    }    public static void main(String[] args) {        SwingUtilities.invokeLater(new Runnable() { public void run() {     new MyWind().setVisible(true); }        });    }}