Problem with changing text in run method

Question

Hi guys
This is just a dummy example. I wanna change the text from "hello" to "goodbye" after i ran the application. Can somebody tell me how to do this, please?
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import java.text.*;
import java.sql.*;
import java.lang.*;
import java.io.*;
import java.awt.color.*;
import java.net.*;
import java.util.*;
import java.awt.Container;
import javax.swing.plaf.basic.*;
import java.lang.Double.*;
public class MyClass extends javax.swing.JFrame implements Runnable{
final Container c = getContentPane();
JPanel panel1 = new JPanel();
JTextField txtfield = new JTextField();
Thread runner = null;
boolean alive = true;
public MyClass(){
super("MyClass");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
panel1.setBounds(new Rectangle(10,10,400,400));
panel1.setLayout(null);
c.add(panel1);
txtfield.setBounds(new Rectangle(20,20,100,100));
panel1.add(txtfield);
public void run(){
while(alive)
txtfield.setText("hello");
public void changeText(){
txtfield.setText("Goodbye");
public void start(){
if (runner==null){
     runner=new Thread(this);
runner.start();
public void stop(){
if(runner!=null)
runner=null;
public static void main(String[] arguments){
MyClass frame = new MyClass();
frame.pack();
frame.setBounds(10,0,400,400);
frame.setVisible(true);
ExitWindow exit = new ExitWindow();
frame.start();
}

Answer 1

Hi,
also it would be helpfull if you have a button or something which can set alive to false, otherwise the thread loops infinitely. Another thing is, that no other thread than the event-handling-thread should change swing components. And third, it would be a good idea, to add a Thread.sleep(1000) or so in the loop to give the event-handling-thread a chance to run also - not all platforms provide preemptive thread switching.
To set a swing component by another thread than the event-handling thread you should do the following:
Runnable r = new Runnable() {
public void run() {
// here the components setup
SwingUtilities.invokeLater(r);this way the manipulation of the swing component is done by the event-handling-thread instead.
greetings Marsian