下面 Java 程序的输出结果可能是（）

class MyThread1 extends Thread {

  public void run() {
    Test.n1 = Test.n2;
    Test.n2 = -1;
  }
}

class MyThread2 extends Thread {

  public void run() {
    Test.n2 = Test.n1;
    Test.n1 = -1;
    System.out.printf("%d %d\n", Test.n1, Test.n2);
  }
}

public class Test {

  public static int n1 = 0;
  public static int n2 = 1;

  public static void main(String[] args) {
    MyThread1 t1 = new MyThread1();
    MyThread2 t2 = new MyThread2();
    t1.start();
    t2.start();
  }
}