Executors.新SingleThreadExecutor()テスト

public class Qiao3 {
    public static void main(String[] args) {
        Thread thread1 = new Thread(()->{
            System.out.println("111");
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("222");
        });
        Thread thread2 = new Thread(()->{
            System.out.println("333");
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("444");
        });
        Thread thread3 = new Thread(()->{
            System.out.println("555");
            try {
                Thread.sleep(5000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println("666");
        });
        ExecutorService executorService = Executors.newSingleThreadExecutor();
        executorService.execute(thread1);
        executorService.submit(thread2);
        executorService.execute(thread3);
        System.out.println("ok");

    }
}