java join阻碍线程

public class Demo {

    public static void main(String[] args) throws Exception {

       System.out.println("main start");

        Thread t1 = new Thread(() -> {

            System.out.println("t1 start");

            System.out.println("t1 end");

        });

        t1.start();

        t1.join();

        System.out.println("main end");

    }

}