Coding interview questions and answers
These sample Coding interview questions are customized for different programming languages and can be used to test candidates on general coding and language-specific criteria. Use these programming questions to evaluate candidates’ skills and hire the best programmers for your company.
10 good coding interview questions
- Describe the process of writing a piece of code from requirements to delivery.
- Which tools have you used to test your code quality?
- How can you debug a program while it’s being used?
- What’s your favorite programming language and why? What features (if any) would you like to add to this language?
- Where do you place most of your focus when reviewing somebody else’s code?
- How do you stay up-to-date with the latest technology developments?
- What is the difference between String, StringBuilder and StringBuffer in Java?
- Can you explain circular dependencies in Python and potential ways to avoid them?
- What’s the difference between the include() and require() functions in PHP?
- Can you describe the difference between inline elements and block elements in HTML/CSS?
Here are 10 essential interview questions and sample answers to help identify the best candidates for this role.
Describe the process of writing a piece of code from requirements to delivery.
This question evaluates the candidate’s understanding of the software development lifecycle.
Sample answer:
“I start by understanding the requirements and breaking them down into smaller tasks. Then I write the code, followed by unit testing. After that, I integrate and perform system testing before the final delivery.”
Which tools have you used to test your code quality?
This question assesses the candidate’s familiarity with code quality tools.
Sample answer:
“I’ve used tools like JUnit for Java, PyTest for Python, and ESLint for JavaScript to ensure code quality.”
How can you debug a program while it’s being used?
This question tests the candidate’s debugging skills in real-time scenarios.
Sample answer:
“I would use logging and monitoring tools to identify issues without affecting the user experience.”
What’s your favorite programming language and why? What features (if any) would you like to add to this language?
This question gauges the candidate’s preferences and their understanding of programming languages.
Sample answer:
“I love Python for its readability and versatility. However, I wish it had better multi-threading support.”
Where do you place most of your focus when reviewing somebody else’s code?
This question evaluates the candidate’s code review practices.
Sample answer:
“I focus on code readability, efficiency, and whether it adheres to best practices.”
How do you stay up-to-date with the latest technology developments?
This question assesses the candidate’s commitment to continuous learning.
Sample answer:
“I follow tech blogs, participate in online forums, and attend industry conferences.”
What is the difference between String, StringBuilder and StringBuffer in Java?
This question tests the candidate’s knowledge of Java’s string handling.
Sample answer:
“String is immutable, while StringBuilder and StringBuffer are mutable. StringBuffer is thread-safe, unlike StringBuilder.”
Can you explain circular dependencies in Python and potential ways to avoid them?
This question evaluates the candidate’s understanding of Python’s dependency management.
Sample answer:
“Circular dependencies occur when two modules depend on each other. To avoid this, you can use import statements wisely or refactor the code.”
What’s the difference between the include() and require() functions in PHP?
This question tests the candidate’s knowledge of PHP’s file inclusion mechanisms.
Sample answer:
“Both are used for file inclusion, but require() will produce a fatal error if the file is not found, while include() will only produce a warning.”
Can you describe the difference between inline elements and block elements in HTML/CSS?
This question assesses the candidate’s understanding of HTML/CSS styling.
Sample answer:
“Inline elements do not start on a new line and only take up as much width as necessary. Block elements take up the full width and start on a new line.”
What does a good coding candidate look like?
A strong coding candidate will have a deep understanding of multiple programming languages, excellent problem-solving skills, and a commitment to producing high-quality code.
How to use programming questions to test candidates
Most engineers and developers are required to know how to code. Evaluate candidates’ knowledge using coding skills interview questions during the hiring process. For junior positions, ask basic coding interview questions and test candidates theoretical knowledge using simple exercises. For more senior engineering roles, opt for a written assignment, where you can assess how candidates approach coding projects end-to-end.
Asking too many programming technical interview questions can overwhelm candidates. During a programming interview, focus on specific languages that you want to test for, based on your needs. For example, choose between java coding interview questions and python coding interview questions depending on the role you’re hiring for.
For all engineering positions, look for candidates who blend a Computer Science academic background with IT work experience. Keep an eye for candidates who are enthusiastic about coding and can find workarounds to coding issues. Award bonus points to candidates who keep up with the latest developments in coding and technology.
Let’s summarize some of the questions and add a few more divided into specific types.
General programming interview questions
- Describe the process of writing a piece of code from requirements to delivery.
- Which tools have you used to test your code quality?
- How can you debug a program while it’s being used?
- What’s your favorite programming language and why? What features (if any) would you like to add to this language?
- Where do you place most of your focus when reviewing somebody else’s code?
- How do you stay up-to-date with the latest technology developments?
For more examples, see our full Programming interview questions list.
Java coding interview questions
- How are Runtime exceptions different from Checked exceptions?
- Why use an object Factory and how would you implement the Singleton pattern?
- Is this possible in Java? “A extends B, C”
- What is the difference between String, StringBuilder and StringBuffer in Java?
For more examples, see our full Java Developer interview questions or Java Software Engineer interview questions lists.
Ruby coding interview questions
- What is the use of load and require in Ruby?
- Explain each of the following operators and how and when they should be used: ==, ===, eql?, equal?
- What is a module? Can you tell me the difference between classes and modules?
- What are some of your favorite gems?
For more examples, see our full Ruby Developer interview questions list.
Python coding interview questions
- Why are functions considered first class objects in Python?
- Can you explain circular dependencies in Python and potential ways to avoid them?
- Give an example of filter and reduce over an iterable object.
- Can you explain the uses/advantage of a generator?
For more examples, see our full Python Developer interview questions list.
.NET coding interview questions
- What is the WebSecurity class in .NET? What is its use?
- In .NET, attributes are a method of associating declarative information with C# code. Please describe the way they are used and a proper use case.
- Which is the best way to pass configuration variables to ASP.NET applications?
- Is it possible in .NET to extend a class (any class) with some extra methods? If yes, how can it be accomplished?
For more examples, see our full .NET Web Developer interview questions list.
PHP coding interview questions
- If you need to generate random numbers in PHP, what method would you follow?
- What’s the difference between the include() and require() functions?
- Explain how you develop and integrate plugins for PHP frameworks, like Laravel and Yii.
- How can you get web browser’s details using PHP?
For more examples, see our full PHP Developer interview questions list.
HTML/CSS coding interview questions
- Can you describe the difference between inline elements and block elements?
- Why is it generally a good idea to position CSS <link>s between <head></head> and JS <script>s just before </body>? Do you know any exceptions?
- Can you describe how padding and margin differ?
- How is responsive design different from adaptive design?
For more examples, see our full HTML interview questions list.
JQuery interview questions
- How would you delete cookies in JQuery?
- What are the basic JQuery selectors and how do you use them?
- Is there a difference between jquery.size() and jquery.length?
- What are the advantages of JQuery?
JavaScript interview questions
- Which are the different types of variables?
- What is the pop()method in JavaScript?
- What’s a “closure” in JavaScript?
- Can you explain how you would clone an object?