One, create a new thread
Creating a new thread is very simple. After initialization, you can enable the start() method.
Thread t1 = new Thread（）； t1.start()；
So what to do after thread start(). Thread also has a run() method, start will create a new thread to execute the run method.
t1.run(); The run method is executed in the current thread.
Note: Do not use the run method to start a new thread, it will only execute the code in the run() method serially in the current thread.