Java Swing--事件

不明白的是这句：final JButton jb=new Button();,为什么要加final,final在这里的作用是什么呢？

import java.awt.event.ActionEvent;import java.awt.event.ActionListener;import javax.swing.*;public class MySwing extends JFrame{private int count;private JButton jb;  public MySwing(){count=0;final JButton jb=new JButton();this.setTitle("创建按钮");jb.setText("按钮按下了0次");jb.setMnemonic('a');this.add(jb);jb.addActionListener(new ActionListener(){@Overridepublic void actionPerformed(ActionEvent e) {// TODO Auto-generated method stubjb.setText("按钮按下了"+(++count)+"次");}});this.setBounds(300, 250, 300, 200);this.setVisible(true);}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubMySwing s=new MySwing();}}