TIme taken by Child threads to execute

Question

Hi
I have a small query related to multithreading. I have a main thread launching a few Child threads. Now I want to check how much time all the 10000 child threads are taking to execute. I cannot write a System.currentTimeMillis(); before a main thread exits because I want the Child threads to keep executing even after the Main thread exits because I do not know how much time the child threads will take. I have made the child threads as non-deamon
class ChildThread implements Runnable {
     Thread t;
     int i;
     ChildThread(int i) {
          t = new Thread(this, "SMS Thread");
          this.i = i;
          t.setDaemon(false);
          t.start();
     public void run() {
          try {
               System.out.println(i);
          } catch (Exception smsex) {
               System.out.println("Exception occured while sending message :"
                         + smsex.getMessage());
               smsex.printStackTrace();
public class MainThread {
     public static void main(String args[]) {
          long start = System.currentTimeMillis();
          ChildThread thread = null;
          try {
               for (int i = 10000; i > 0; i--) {
                    thread = new ChildThread(i); // create a new thread
          } catch (Exception e) {
               System.out.println("Main thread interrupted.");
          long end = System.currentTimeMillis();
          System.out.println("Main thread exiting. Took " + (end - start)
                    + " ms.");
}

Answer 1

This is a sample i have assumed.. dont have the complete code.
I will just explain this
Create an executor service object in a class called ThreadDispatcher.
And create your chileThread as given below
class ChildThread implements Runnable {
     ChildThread() {                    
     public void run() {
          try {
               System.out.println(i);
          } catch (Exception smsex) {
               System.out.println("Exception occured while sending message :"
                         + smsex.getMessage());
               smsex.printStackTrace();
}And the ThreadDispatcher class as below -This is just to beautify the code :)
public class ThreadUtil {
private static ExecutorService exec = Executors.newFixedThreadPool(some_value);
public static List<Future> executionResults = new ArrayList<Future>();
}And finaly come to the main Thread class
public class MainThread {
     public static void main(String args[]) {
          ChildThread thread = null;
          try {
                         long start = System.currentTimeMillis();
               for (int i = 10000; i > 0; i--) {
                    thread = new ChildThread(i); // create a new thread
                                ThreadDispatcher.executionResults.add(ThreadDispatcher.exec.submit(thread));
          } catch (Exception e) {
               System.out.println("Main thread interrupted.");
                //Here place the while loop to check each thread status
                 while (ThreadDispatcher.executionResults.size() > 0) {
               try {
                    Future task = ThreadDispatcher.executionResults.get(0);
                    task.get();//Wait until the thread finishes execution
                                ThreadDispatcher.executionResults.remove(task);
               } catch (InterruptedException e) {
                    e.printStackTrace();
               } catch (ExecutionException e) {
                    e.printStackTrace();
          long end = System.currentTimeMillis(); //This time will probably be the end time.
          System.out.println("Main thread exiting. Took " + (end - start)
                    + " ms.");
}Hope this will be helpful...