Java 线程是在用户空间还是在内核空间中创建的？

查看此代码

    Thread t1 = new Thread(new Runnable() {

        @Override
        public void run() 
        {
            try
            {
                System.out.println("STARTING SERVER...");
                ServerSocket s = new ServerSocket(2544);
                System.out.println("SERVER BLOCKED ON ACCEPT");
                Socket ss = s.accept();
                System.out.println("SERVER NOT BLOCKED ANYMORE");
            }
            catch(Exception ex)
            {
                ex.printStackTrace();
            }
        }
    });
    t1.start();



    Thread t2 = new Thread(new Runnable() {

        @Override
        public void run() 
        {
            try
            {
                while(true)
                {
                    Thread.sleep(1000);
                    System.out.println("Hello");
                }
            }
            catch(Exception ex)
            {
                ex.printStackTrace();
            }
        }
    });
    t2.start();

输出：

STARTING SERVER...
SERVER BLOCKED ON ACCEPT
Hello
Hello
Hello
Hello
Hello
Hello
Hello
...

Java线程应该是用户空间线程，对吧？因此，一个阻塞的线程应该阻塞整个过程...事实并非如此。他们发生了什么？