Threading- Can I call methods from specific threads or from all in a group?

Question

I've just recently started working with threads. I've done a lot of searching and reading but I haven't seen the specific questions I'm wondering answered. Of course, it's about communication.
The amount of newly created threads that will exist is indefinite. Sometimes I'll have one, sometimes ten. So I'll just call them t1 - t9. When I create them, I add them to a ThreadGroup - tg.
This project contains 2 class files, Main and ThreadClass. I'll post all of the code so you can see what I'm doing.
public class Main {
    public static void main(String[] args) {
        for (int i = 1; i < 10; i++) {
            ThreadGroup tg = new ThreadGroup("tg1");
            Thread t = new Thread(tg, new ThreadClass("t" + i));
            t.start();
public class ThreadClass extends Thread {
    public ThreadClass(String name) {
        super(name);
    public void run() {
        System.out.println("New Thread - " + getName());
        while (true) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                System.out.println("Exception: " + e);
    public void printText() {
        System.out.println("Printing text from " + getName());
}So whenever a new thread is created, it prints "New Thread - [ThreadNameHere]". But I also have printText() in ThreadClass that has not been used yet and that is what I really want to accomplish. Is there a way to call printText() by the thread group (tg1 in this case) so it is executed across all threads that belong to the group? Is there a way to call printText() in a specific thread from my Main class, such as "t3"?
Thank you for your help!
Edited by: sdouble on Sep 9, 2008 10:10 AM - Fixed a typo

Answer 1

Yes, usually you want to implement Runnable, not extend Thread. You're not adding new functionality to Threads or making some kind of more-specific version of them.
You can get each thread in your ThreadGroup back out into an array by using one of the varients of Enumerate, but nothing stops you from just putting your objects (that implement Runnable) into an ArrayList or any collection of your own that you want to as you make them, and then later iterating over it and calling the method that you want.
Something like this...
public class MyThread implements Runnable {
   public void run() { ... }
   public void printStuff() { ... }
public static void main(String[] args) {
   MyThread a = new MyThread();
   MyThread b = new MyThread();
   ArrayList threadList = new ArrayList();
   threadList.add(a);
   threadList.add(b);
   for(MyThread thread : threadLIst) {
      thread.printStuff();
}