Redirecting system.out to a file

Question

I want to have the output of these threads go to a file, which it is doing now, but the program is finishing before all the data is written to the file.
I had another idea that the threads could write to a shared stringbuffer and then when they have finished, i could write the contents of that stringbuffer to a file, but when do it tell it to write to the file. how can i tell when the threads are finished.
/*      12 Nov 2002
     Class extends PThread which extends Thread.
import Concurrency.*;
import java.io.*; //added to write output to a file
public class Exercise1 extends PThread{
     private static File theOutputFile;
     private static FileWriter fileWriterStream;
     private static int counter = 0;
     public Exercise1() {
          try {
               if(theOutputFile == null) {
                    theOutputFile = new File("output.txt");
                    fileWriterStream = new FileWriter(theOutputFile);
          }catch(IOException ioe){}     
     public static void main(String[] args) throws IOException {
          System.out.println("Dave Casserly\n" +
                                   "Check the source folder for a file called output.txt\n" +
                                   "This contains the programs output.\n");
          Exercise1 thread1 = new Exercise1();
          Exercise1 thread2 = new Exercise1();
          thread1.start();
          thread2.start();
     //each thread will look at counter make sure its less than 1000,
     //get the current counter value and increment it
     //print it to screen
     //then increment the static counter
     public void run(){
          try {
               while(counter <= 1000) {
                    int count = counter;
                    count++;
                    counter++;
                    System.out.println("COUNT = " + count);                    //write to screen
                    fileWriterStream.write("COUNT = " + count + "\n");      //write to file
                    counter = count;     
          }catch(IOException io){}     
}//end of class

Answer 1

You need to join the main thread with the child threads.
Something like this:
  Exercise1 thread1 = new Exercise1();
  Exercise1 thread2 = new Exercise1();
  thread1.start();
  thread2.start();
  thread2.join();
  thread1.join();Or something.