1번코드

public class NumberPrinter implements Runnable{
 private static final int REPETITIONS = 100;
 private static final int DELAY = 1000;

 private int number;
 public NumberPrinter(int n) { number = n; }

 public void run() {
  try{
   for (int i = 1; i <= REPETITIONS; i++){
    Thread t = Thread.currentThread();
    String name = t.getName();
    System.out.println(name + \": \" + i);
    Thread.sleep(DELAY);        
   }
  }
  catch (InterruptedException exception) {}
 }
}

public class NumberThreadRunner{
 public static void main(String[] args)   {

  NumberPrinter r1 = new NumberPrinter(0);
  Thread t1 = new Thread(r1);
  t1.setName(\"t1\");

  Thread t2 = new Thread(r1);
  t2.setName(\"t2\");

  t1.start();
  t2.start();
 }
}

2번 코드
public class NumberPrinter implements Runnable{
 private static final int REPETITIONS = 100;
 private static final int DELAY = 1000;

 private int number;
 public NumberPrinter(int n) { number = n; }

 public void run() {
  try{
   for (int i = 1; i <= REPETITIONS; i++){
    Thread t = Thread.currentThread();
    String name = t.getName();
    System.out.println(name + \": \" + ++number);
    Thread.sleep(DELAY);        
   }
  }
  catch (InterruptedException exception) {}
 }
}

public class NumberThreadRunner{
 public static void main(String[] args)   {

  NumberPrinter r1 = new NumberPrinter(0);
  Thread t1 = new Thread(r1);
  t1.setName(\"t1\");

  Thread t2 = new Thread(r1);
  t2.setName(\"t2\");

  t1.start();
  t2.start();
 }
}

3번코드
public class NumberPrinter implements Runnable{
 private static final int REPETITIONS = 100;
 private static final int DELAY = 1000;

 private int number;
 public NumberPrinter(int n) { number = n; }

 public void run() {
  try{
   for (int i = 1; i <= REPETITIONS; i++){
    Thread t = Thread.currentThread();
    String name = t.getName();
    System.out.println(name + \": \" + ++number);
    Thread.sleep(DELAY);        
   }
  }
  catch (InterruptedException exception) {}
 }
}

public class NumberThreadRunner{
 public static void main(String[] args)   {

  NumberPrinter r1 = new NumberPrinter(0);
  Thread t1 = new Thread(r1);
  t1.setName(\"t1\");

  NumberPrinter r2 = new NumberPrinter(0);
  Thread t2 = new Thread(r2);
  t2.setName(\"t2\");

  t1.start();
  t2.start();
 }
}


이렇게 코드 3개가 각각 어떻게 다르고, 어떨때 어떤 코드 쓰는지좀 설명해줄수 있어?