ref:
java中产生死锁的原因及如何避免
https://blog.csdn.net/m0_38126177/article/details/78587845
java如何避免死锁
http://www.cnblogs.com/vinozly/p/5240204.html
ref:
https://blog.csdn.net/m0_38126177/article/details/78587845
http://www.cnblogs.com/vinozly/p/5240204.html