编写线程，模拟上课情形，三个学生在课堂上睡觉，三个学生分别打算睡10分钟，20分钟，30分钟，当老师准备上课时，老师叫醒了第一个和第二个同学，第一个同学醒后叫醒第三个同学-Writing thread, simulated class situation, three students to sleep in class, three students were going to sleep 10 minutes, 20 minutes, 30 minutes, when the teacher