例子中包含了两种创建线程的方法：一种是创建用户自己的线程子类，另一种是在用户自己的类中实现Runable接口。线程优先级以及同步。 -Two examples are included to create threads: one is to create your own thread subclass, the other is a user interface to achieve Runable own class. Thread priority and synchronizati