行getTask()，要从阻塞队列中获取任务来执行。也就是说：任务被执行的第一种可能就是指线程被创建时带有firstTask任务，会先执行掉firstTask。
https://www.douban.com/group/topic/187672588/
https://www.douban.com/group/topic/187672588
https://www.douban.com/group/topic/187672588/?type=rec
https://www.douban.com/group/topic/187672588/?type=like
https://www.douban.com/group/topic/187672588/?type=collect
https://www.douban.com/group/topic/187672682/
https://www.douban.com/group/topic/187672682
https://www.douban.com/group/topic/187672682/?type=rec
https://www.douban.com/group/topic/187672682/?type=like
https://www.douban.com/group/topic/187672682/?type=collect
https://www.douban.com/group/topic/187672695/
https://www.douban.com/group/topic/187672695
https://www.douban.com/group/topic/187672695/?type=rec
https://www.douban.com/group/topic/187672695/?type=like
https://www.douban.com/group/topic/187672695/?type=collect
https://www.douban.com/group/topic/187672720/
https://www.douban.com/group/topic/187672720
https://www.douban.com/group/topic/187672720/?type=rec
https://www.douban.com/group/topic/187672720/?type=like
https://www.douban.com/group/topic/187672720/?type=collect
https://www.douban.com/group/topic/187672735/
https://www.douban.com/group/topic/187672735
https://www.douban.com/group/topic/187672735/?type=rec
https://www.douban.com/group/topic/187672735/?type=like
https://www.douban.com/group/topic/187672735/?type=collect
https://www.douban.com/group/topic/187672752/
https://www.douban.com/group/topic/187672752
https://www.douban.com/group/topic/187672752/?type=rec
https://www.douban.com/group/topic/187672752/?type=like
https://www.douban.com/group/topic/187672752/?type=collect
https://www.douban.com/group/topic/187672774/
https://www.douban.com/group/topic/187672774
https://www.douban.com/group/topic/187672774/?type=rec
https://www.douban.com/group/topic/187672774/?type=like
https://www.douban.com/group/topic/187672774/?type=collect
https://www.douban.com/group/topic/187672786/
https://www.douban.com/group/topic/187672786
https://www.douban.com/group/topic/187672786/?type=rec
https://www.douban.com/group/topic/187672786/?type=like
https://www.douban.com/group/topic/187672786/?type=collect
https://www.douban.com/group/topic/187672803/
https://www.douban.com/group/topic/187672803
https://www.douban.com/group/topic/187672803/?type=rec
https://www.douban.com/group/topic/187672803/?type=like
https://www.douban.com/group/topic/187672803/?type=collect
https://www.douban.com/group/topic/187672815/
https://www.douban.com/group/topic/187672815
https://www.douban.com/group/topic/187672815/?type=rec
https://www.douban.com/group/topic/187672815/?type=like
https://www.douban.com/group/topic/187672815/?type=collect
https://www.douban.com/group/topic/187672839/
https://www.douban.com/group/topic/187672839
https://www.douban.com/group/topic/187672839/?type=rec
https://www.douban.com/group/topic/187672839/?type=like
https://www.douban.com/group/topic/187672839/?type=collect
https://www.douban.com/group/topic/187672857/
https://www.douban.com/group/topic/187672857
https://www.douban.com/group/topic/187672857/?type=rec
https://www.douban.com/group/topic/187672857/?type=like
https://www.douban.com/group/topic/187672857/?type=collect
https://www.douban.com/group/topic/187672867/
https://www.douban.com/group/topic/187672867
https://www.douban.com/group/topic/187672867/?type=rec
https://www.douban.com/group/topic/187672867/?type=like
https://www.douban.com/group/topic/187672867/?type=collect
https://www.douban.com/group/topic/187672884/
https://www.douban.com/group/topic/187672884
https://www.douban.com/group/topic/187672884/?type=rec
https://www.douban.com/group/topic/187672884/?type=like
https://www.douban.com/group/topic/187672884/?type=collect
https://www.douban.com/group/topic/187672906/
https://www.douban.com/group/topic/187672906
https://www.douban.com/group/topic/187672906/?type=rec
https://www.douban.com/group/topic/187672906/?type=like
https://www.douban.com/group/topic/187672906/?type=collect