Concurrency:
Thread: 1.Thread.yield (), thread.join () function and the difference? Execution Thread.yield () the current thread to make the cpu, the state becomes a ready state from running state. Execution thread.join () the current thread is blocked waiting for thread execution logic behind after the completion.
2. Thread state and conversion: New, Runnable, Running, Terminated, Blocked, Waiting, Timed_Waiting 
Reproduced in: https: //my.oschina.net/u/2250599/blog/3059664