// 多条件排序第二个写法，先按Age排序，再根据Salary排序
listDevs.sort(Comparator.comparing(Developer::getAge).thenComparing(Developer::getSalary));
https://my.oschina.net/sdlvzg/blog/2243766
http://www.blogjava.net/ocean07000814/articles/297940.html