JavaGUI实现点名系统

有一个名字数组，根据线程知识是框中的数据依次修改

package Week1008;
 
import java.awt.Font;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
 
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
 
public class Main extends Thread implements ActionListener {
	String[] s= {1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20};
		JFrame frame=new JFrame("点名使用");
		JButton btn=new JButton("停止");
		JTextField tf=new JTextField();
		public Main(){
			frame.setLayout(null);
			frame.setBounds(300, 400, 300, 350);
			tf.setBounds(100, 40, 120, 30);
			tf.setFont(new Font("Monospaced", 23, 30));
			btn.setBounds(80, 120, 150, 100);
			frame.add(btn);
			frame.add(tf);
			frame.setVisible(true);
			btn.addActionListener(this);
		}
		public void run(){
			for(int i=1;i<=20;i++){
 
				tf.setText(s[i-1]);
				try {
					sleep(50);
				} catch (InterruptedException e) {
					e.printStackTrace();
				}
				if(i==20)i=1;
			}
		}
		public void actionPerformed(ActionEvent e) {
			if(e.getSource()==btn){
				if(btn.getText().equals("开始")){
					this.resume();
					btn.setText("停止");
				}
				else if(btn.getText().equals("停止")){
					//this.stop();
					this.suspend();
					btn.setText("开始");
				}
				}
			}
		public static void main(String[] args) {
			Main m=new Main();
			m.start();
		}
}