Asking Knowledge Questions during Job Interviews

I posted a riddle in Java yesterday that showed two examples of Static members in an Inner-class, one compiled correctly, the other not. You can check out the answer in the comments. I also wrote in the post that this is "guaranteed to make people mumble in job interviews". Several readers complained that this would make a terrible job interview question. I beg to differ.

For starters, one should remember that a job interview is not a test. In most standard written tests, the goal is to provide the correct answer. Each correct answer is worth some points. The more you answer correctly, the higher your score. Tests are good tools for assessing knowledge and, to some degree, intelligence. 

In a job interview, it's different. The goal is to asses the candidate and form an impression. Asking questions and grading the correctness of the answer is important, but it's not the main issue. It's not just getting to the target, it's how you get there (or not). In the interview, you want to detect other factors like: personality, communication skills, creativity, positive thinking and resourcefulness. I found myself more than once approving people who fail to solve a question and disqualifying people who answered correctly.

I gathered just a few examples of what a candidate might do with the question I presented and how you may proceed and interpret the behavior (the next section is written in male form for convenience).

The candidate is puzzled and has no idea

Ask the candidate what he would do next in a real situation. If he does not know that's a bad sign of somebody who would come running to you on every problem. Problem solving skills are one of the main characteristics of a good developer.

He wants to search the web

Let him, but only if he asks. This shows creativity and thinking outside the box: I can search Google during my interview. Knowing how to find answers over the web is an important skill. Many of the experienced developers are so good at it that they take it for granted. Don't just give him time to search the web. Do it with him. See how he works in real situations. Is he cleaver enough to search for the right terms and sift through the search results? This is where intelligence and experience comes into play.

The candidate may offer some wrong answers

Listen carefully and interact. Engage in a discussion. You'll get a good idea on how intimately he knows Java. He may give an explanation which contradicts the basics of the language and demonstrate complete misunderstanding of the concepts. The purpose is to test understanding and experience not memorizing the spec.

The candidate protests about the question

That is an acceptable reaction, I would expect that from "hot shots". There comes a time in a developers' job where he will be asked to do things which he may not like. That will give you some idea of how he's going to react in that situation. 

The candidate decides that it's not an acceptable question and refuses to answer

It may indicate that the candidate has an inflated ego, as he feels this question does not dignify an answer. I'm not saying he won't make a good developer, but it would tell you something about his abilities as a team player.  

I tried to think of some possible scenario, clearly, there are many others. My point is that this may be a legitimate job interview question, and not because it checks the candidate ability to memorize a spec, but because it may provide new insights regarding the candidate, insights which may be different from those you would get from the other questions you'd normally use.