JAVA之多线程入门和自动滚轮

start实现每1s递增的在textarea打印一个数字，end实现终止start的线程

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Graphics;
import java.awt.Point;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.net.URL;
import java.util.Random;

import javax.swing.ImageIcon;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingConstants;
import javax.swing.WindowConstants;
import javax.swing.table.DefaultTableModel;

public class test extends JFrame{
JTextArea jt = new JTextArea(10,10);
JButton jb_s = new JButton("start!");
JButton jb_e = new JButton("end!");
JScrollPane js = new JScrollPane(jt);
Thread t1 ,t2;
int count = 0;
boolean flag = true;

public test(){
init();

jb_s.addActionListener(new ActionListener() {
@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
flag = true;
jt.setLineWrap(true);
jt.setEditable(false);
t1 = new Thread(new Runnable() {
@Override
public void run() {
// TODO Auto-generated method stub
while(flag){
jt.append(count++ + " \n");//
jt.setCaretPosition(jt.getText().length());//方法1：自动滚动到textarea的底部
//js.getViewport().setViewPosition(new Point(0,jt.getLineCount()*20));//方法2
try {
Thread.sleep(100);
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}
}
});
t1.start();
}
});

jb_e.addActionListener(new ActionListener() {

@Override
public void actionPerformed(ActionEvent arg0) {
// TODO Auto-generated method stub
t2 = new Thread(new Runnable() {

@Override
public void run() {
// TODO Auto-generated method stub
flag = false;
}
});

t2.start();
}
});
}

public void init(){
setLocationRelativeTo(null);
Container con = getContentPane();
con.add(js,BorderLayout.NORTH);

JPanel jp = new JPanel();
jp.setLayout(new FlowLayout());
jp.add(jb_s);
jp.add(jb_e);
jp.setOpaque(false);
con.add(jp,BorderLayout.SOUTH);

setVisible(true);
setSize(500,300);
setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
}

public static void main(String[] agrs){
new test();
}
}