Java.lang.IllegalThreadStateException cause resolution--the same thread cannot call the Start method repeatedly

A few days ago wrote a small program, run the time found in the loop the second time there is a java.lang.IllegalThreadStateException exception
Through the Internet query found that the same thread can not repeatedly call the Start method, make the following changes:
Change your defined Sellticket extends thread class to Sellticket implements Runnable, and then use the new Thread (robot). Start can start multiple times.

Java.lang.IllegalThreadStateException cause resolution--the same thread cannot call the Start method repeatedly