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(){

			@Override
			public void actionPerformed(ActionEvent e) {
				// TODO Auto-generated method stub
				jb.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 stub
		MySwing s=new MySwing();
	}

}