下面是我的onsite 面经：http://www.1point3acres.com/bbs/ … p;page=1#pid1956961
我感觉对于OOP设计问题，关键要和面试官进行讨论，弄清情景situation ，who will use it,在这个situation都是有哪些对象，他们在干什么，他们之间是什么关系，然后一个对象一个对象的去分析这个对象应有的属性，和行为。多和面试官讨论，越细致越好！如果可以使用什么单例，或者factory method 来设计的话，multi threading, 就尽量的添加上这些东西。
First ask the interviewer what kind of elevator? there is only one elevator serving that building or multiple elevators serving the building simultaneously?
this situation is that: there is one elevator serving the building. there are many floors in the buliding. Maybe there are some users in different floor pressing the button simultaneously. This results in some requests to RequestProcessCenter for processing. The RequestProcessCenter figure out the first request that need to be processed in such an algorithm that the distance between target floor and current floor is shortest.