java programming

public class FileSync {
  private File outFile;
  private PrintStream outStream;

  public FileSync() throws IOException {
      outFile = new File("c:/orisree/java/ran.txt");
      outStream = new PrintStream(new FileOutputStream(outFile));
  }

  public Object getSyncObject() {
      return outFile;
  }

  public void writeToFile(String text) throws IOException {
      outStream.println(text);
  }
}
**************************************************
public class TestSynch extends Thread {

  public TestSynch() {
  }
  public static void main(String[] args) {
      WriteThread[] threads = new WriteThread[3];
      try {
          for(int i = 0; i < threads.length; i++) {
              threads[i] = new WriteThread();
          }

          for(int i = 0; i < threads.length; i++) {
              threads[i].start();
          }

      }catch(IOException ioe) {
          ioe.printStackTrace(System.err);
      }
  }
}
***************************
public class WriteThread extends Thread {
  private static int threadCount;
  private int threadNum;
  private FileSync fileSync;

  static {
      threadCount = 0;
  }

  public WriteThread() throws IOException {
      threadNum = ++threadCount;
      fileSync = new FileSync();
  }

  public void run() {
      Object syncObject = fileSync.getSyncObject();
      synchronized(syncObject) {
          for(int i = 0; i < 100; i++) {
              try {
                  fileSync.writeToFile("Printing from thread " + threadNum + " line " + i);
              }catch(IOException ioe) {
                  ioe.printStackTrace(System.err);
              }
          }
      }
  }
}



From the above 3 classes,when i run TestSynch i get output , for 1 to 21, i get threadnum=1
then from 22 to 54, i get threadnum=3 ,after that until 99 i get threadnum=1,
How does synchObject allow thread 3 to come in between thread 1.pls give me the answer at the earliest.
Urgent..