How to know when mutiple threads have stopped?

Question

Hi all,
I have a for loop in which multiple threads are started.Now I want to perform a UI action when all the threads have returned.But i am not able to make it out as when have all the threads returned.Can anyone help me out with it?
Regards,
Mansi
Edited by: MansiSachar on Sep 1, 2008 11:33 PM

Answer 1

Two methods I can quickly think of that will help you,
I am sure that there is better ways of doing it just to lazy to check for and do them.
method 1): Interface
method 2): Runnable - run()--------------------
publc interface MyThreadListener{
  public void threadGroupStarted();
  public void threadGroupFinnished();
pubilc class GUI extends JFrame implements MyThreadListener{
  private MyOtherThread mot = null;
  public GUI(){
    init();
    mot = new MyOtherThread(this);
  public void threadGroupStarted(){
    System.out.println("Threads Started");
  public void threadGroupFinnished()
    System.out.println("Threads Finnished");
  public static void main(String[] args){
    new GUI();
public class MyOtherThread{
  private MyThreadListener mtl = null;
  public MyOtherThread(MyThreadListener mtl){
    this.mtl = mtl;
  public void startNewParallelThread(.....){
//Create a new thread in this class that will do the for(....) join().
//Add the following code:
  mtl.threadStarted();
  for (Thread t : collectionOfThreads){
    t.join();
  mtl.threadFinnished();Creating a listener will enable you the have the second thread tell the first that it has finnished processing.
pubilc class GUI extends JFrame implements Runnable{//better to create a Runnable Object that implement
  private Thread thread = null;
  public GUI(){
    init();
    thread =new Thread(this);
  public void run(){
    threadGroupStarted();
    for (Thread t : collectionOfThreads){
      t.join();
    threadGroupFinnished();
  public void threadGroupStarted(){
    System.out.println("Threads Started");
  public void threadGroupFinnished()
    System.out.println("Threads Finnished");
  public static void main(String[] args){
    new GUI();
}