public class MyThread extends Thread
{
private static Object lock = new Object();
...
synchronized (lock)
{
Thread.sleep(1000);
System.out.println(number + "\t" + person.getSurname());
Thread.sleep(1000);
System.out.println(number + "\t" + person.toString());
}
...
That way you will get the same person's surname and toString() in order. You won't enforce strict ordering on the people, person 7 may still go before person 1.