Java Phone Interview: The Complete Guide

Java Phone Interview

Java Phone Interview
I’m a huge fan of using a phone interview at the start of my interviewing process.  As someone trying to recruit it’s important that I have some way of filtering the hundreds of CVs that I get.  I’ve come to accept most people are terrible at writing their CV, or just plain bend the truth, so before I meet them face to face it’s good to speak to them on the phone for 20 minutes to ensure that they do in fact know java, and get an understanding of their background.

As a candidate it’s also an opportunity to make a good first impression.  Many people panic that they won’t be able to do themselves justice over the phone (and indeed, candidates who fail often cite this as a reason), however with a few pieces of key advice from this page you can be sure to come out on top of the pack.

Preparing for your java phone interview

You may be dealing with a recruiter or with the firm directly. Either way, contact them and find out the exact details of the phone interview. You want to be as prepared as you can. Specifically you should ask:

  • How long will it be?
  • What sort of questions will be asked? You’ll be lucky if you get an answer to this, but it’s good to know if the questions are more likely to be technical focused or design focused. Chances are the interview will be technically focused as design interviews are really hard to do without a piece of paper or a whiteboard.  You never know, you might hit lucky and get some gems of information for your research.
  • How many people will be on the call? Who will they be? Phone interviews with one or two people will generally be easier as you can identify who’s who and an understanding of their interests and question style. Above that will make it a little more difficult.

It’s then time to simply to hit the books and get learning. Chances are you’re going to get a lot of “what does this thing in Java do?” type questions, as they’re easy to do over the phone.  They’re not necessarily good questions, but they’re the questions interviewers tend to fall back on.

Make sure that whenever you’ve booked your interview for you have somewhere quiet and private to go.  Make sure you get there 5 minutes before the interviewer is due to call.  There is nothing worse than starting your call flustered because you don’t have a place to do the interview and it leaves a terrible first impression (more on that shortly). As an interviewer I have a limited amount of time; I tend to bunch phone interviews to be back to back or slip them in between meetings.  If you waste 5 minutes then you’re losing an opportunity to impress the interviewer.

Make sure you have a copy of your CV with you. The interviewer will have a copy too and will ask you about it.  Chances are you can’t remember what you wrote on it so have it in front of you as it’s very embarrassing when someone asks you about a part of your CV and you have no idea what they’re talking about.

Also ensure you go in with a pre-prepared list of questions for the end of the interview. You will get asked and it’s important you’re quick off the bat. I want to know that you care about this role and have spent the 30 seconds it takes to look at the job description and that want to know more.  Interviewers (and people in general) are egotistical like that. It doesn’t matter if it’s a simple “I was hoping you could tell me more about the role”; just make sure you don’t spend 5 seconds thinking and you ask it straight away.  Have 2 or 3 questions lined up. It doesn’t matter if you really want an answer, the act of asking is what matters.

It’s also an opportunity to impress and show off. Say you know the people you’re interviewing are really keen on a technology or technique, like Test Driven Development.  Use your questions to promote yourself! “I’m a huge fan of TDD and was wondering how exactly do you use it in your team?”. Or “I’ve always wanted to learn TDD but have never been given the opportunity. I find the concept really exciting. Do you think the learning curve is manageable?”.  This is music to an interviewers ears because you actually care. If I’m doing 3 interviews a day 5 days a week things like this really make a big difference.

Phone interview tips for giving the best impression

When your phone rings, think positive.  Be positive. Sound happy.  As cheesy as this sounds, the old adage of “you have 7 seconds to make a first impression” is right. Although I think it’s more like 4 seconds.  The amount of candidates I call that sounds grumpy and/or uninterested is crazy.  This instantly turns me against you and unless you nail all the questions you’re going to have a hard time getting through.  Conversely, if you pick up the phone, sound excited and tell me you’ve been looking forward to the interview then you’re in my positive books and the interview is yours to win.

Speak slowly. You don’t want to rattle through the interview at lightening pace. But, don’t speak so slowly as to bore the interviewer.  Most importantly, know when to stop.  I’ve had candidates give me 5 minute monologues on Spring before I’ve had to step in.  Being able to craft a succinct answer is a hugely important skill, not just in interviewing but as a java developer.  It takes practice but it is well worth it.  If you’re worried about not answering the question fully, simply say “is that ok or would you like me to continue?”. Chances are the interviewer will have picked up on something you’ve mentioned and will change the direction of the question or ask a new one. If not they may simply ask you to continue and you can keep talking.

Some quick don’ts:

  • Don’t sound bored
  • Don’t chew gum
  • Don’t google answers (we can hear the keyboard)
  • Don’t interrupt the interviewer
  • Don’t be afraid to say you don’t know.  Trying to guess your way through isn’t going to fool anyone. If I’m asking the question I probably know the answer. It’s absolutely fine to say “I don’t know about that, but I’m happy to have a guess if you’d like”. That way everyone knows you’re not trying to lie your way through.  Candidates capable of admitting they don’t know will always get my respect.

How to run a phone interview as the interviewer

What does a good technical phone interview look like?  Pretty much the same as a normal interview, only you’re limited to asking questions that don’t need a pen and paper to explain.  You want to save the big guns for the face to face interviews though; this interview should be just to screen the candidates to check they have the basic skills that you’re looking for.

Most interviewers fall back on core java questions.  Definitely include some of these as I’ve had a number of candidates claim to be java developers but who have clearly not touched a line of code in many years. A couple of core questions around exceptions and collections can easily weed this out.  The phone interview format lends itself well to a more open discussion. The candidate you’re hiring is someone who’s going to come in and help with designs and technology choices. You want someone with ideas and experience.  Do they have opinions or are they just content using what’s put in front of them?  For this purpose I recommend basing the majority of the interview around open ended “Tell me about technology X you have on your CV. What do you think about X? Is it a good choice?” type questions.  This allows a candidate to show off their knowledge if they have it, and by playing devils advocate with their answers- “But why not use technology Y?” you can see if they understand the reasons for choosing a technology and whether those views align with your teams.

What you will get asked during the interview

Due the limitations of the telephone you can be fairly certain that the questions will be based in one of four categories:

  • Core Java: threading, exceptions, data structures & algorithms, object oriented programming etc..  This is the basic stuff you simply need to take the time to learn.  Whether or not they are good questions to ask to determine your ability is irrelevant; most interviews will fall back on this so it’s good to be prepared. Have a look at some of the questions on this site, such as on Java collections.
  • Technology discussion. Have you used technology X (or “I see from your CV you’ve used X), can you tell me about it, what do you think of it.  My default go-to topics are Spring and Hibernate as they have a lot of questions that can lead from the initial one and really go into depth.  They also appear on most people’s CVs. This is the sort of question I prefer to ask as you can get a proper understanding of a candidates knowledge and whether they understand the tools they use, or if they just use them because they’re told.  Look at the core technologies on your CV and figure out what your opinion is on them.  The interviewer most likely won’t care what your opinion is specifically but be interested to know that you can articulate the pros and cons of each side and draw a conclusion.
  • Techniques.  I love asking about these.  Every office works differently; agile vs waterfall (yes, waterfall still exists), TDD/BDD/other DD, programming style etc.  Again, if you have put these on your CV then you need to be sure you have good answers for your experience with them. If your department uses TDD so you’ve put it on the CV but you don’t actually do it you’re going to look bad.  Again review your CV and look at what you’ve listed; come up with strong explanations for each of them and have them on hand.
  • Riddles. This is made up of the google-esque questions like “how many grains of sand are there in the world?”.  It’s good to try and read up on some of these just to get comfortable with answering them, but in reality they’re not something you can do a great amount of study for.  Personally I’m not a big fan of these, but every interviewer is different.

Try not to guess what the interviewer is looking for.  They may intentionally lead you down the wrong path to see if you’re a “yes man”.  Stick to your opinions even if they seem controversial.  Be polite, be honest, and try to engage in an open discussion.  The person on the other side of the phone isn’t a robot so try and engage the human side and have a 2 way discussion.   If a candidate fires a question back at me during their answer I enjoy it.  These conversations should be two way.

After the interview

Normally you should have a pretty good idea of how you’ve done, but don’t fret. I’ve had candidates who thought they’d tanked who were actually really good. Conversely I’ve had terrible people who thought they were brilliant. Simply wait to hear back from them and relax comfortable in the knowledge you’ve done your best.  If you don’t make it through then don’t sweat it.  The fact is that every interviewer is different and has different opinions, every company values different things and you may not fit in there at that time. That’s ok. Just keep applying to different roles.

On top of this there is a human element; maybe the interviewer woke up on the wrong side of the bed, or they haven’t had lunch yet so they’re hungry. It’s terrible to think that this could affect your potential job but it’s a fact of life.  Whatever you do, don’t contest the result.  Emailing back to try and explain something better now you’ve had time to think about it or asking to be seen again isn’t going to work and may damage your reputation. The industry is surprisingly small (particularly thanks to LinkedIn) so hold your head high, take the time to review what you could have done better for next time and move on.


Hopefully you’re now feeling more confident about your upcoming interview.  If you have any questions that aren’t covered here then why not drop me an email at, or leave a comment below?


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