main線程列印100此次“main”，新線程列印50次“new”。

public class MyRunnable implements Runnable {
  public void run() {
    for (int i = 0; i < 50; i++) {
      System.out.println("new");
    }
  }
  public static void main(String[] args) {
    new Thread(new MyRunnable()).start();
    for (int i = 0; i < 100; i++) {
      System.out.println("main");
    }
  }
}