线程拾遗 参考博文: 自定义线程池: https://www.cnblogs.com/nele/p/6502750.html https://blog.csdn.net/RichieZhu/article/details/79499638 join方法: https://www.cnblogs.com/lcplcpjava/p/6896904.html 守护线程: https://www.cnblogs.com/lixuan1998/p/6937986.html