Programming Interview Questions And Answers

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    Tech hiring is not easy. But we’ve tried to make it a tad bit easier with a handy bunch of ready-to-be-asked questions.

    These questions will help assess a candidate’s skills and knowledge objectively. Also, preparing in advance and having a well-structured interview process helps interviewers lead the interview impressively and have clarity on what to look for.

    Common Programming Interview Questions

    It is good to assess programming skills when hiring programmers along with other skills like communication and leadership.


    1: What do you think are the essential traits of a good programmer?

    Good programmers:

    1. Exhibit strong problem-solving skills and think critically about how to approach a problem.

    2. Understand and analyze code and can also troubleshoot and debug code.

    3. Think logically and know how to apply the principles of logic to coding.

    4. Constantly look for ways to learn new technologies and improve their skills.

    5. Communicate ideas effectively and collaborate with other team members.

    6. Think creatively to come up with new solutions and ideas.

    7. Have the patience/perseverance to work through difficult or complex issues.

    8. Adapt to changes in technology and new programming languages.

    9. Show a genuine passion for coding and are eager to learn and improve.

    These traits help programmers write efficient, maintainable, and secure code. This is crucial in today’s fast-paced and constantly evolving tech environment.

    2: How will you explain something technical to a non-technical colleague?

    To explain technical concepts to a non-technical person, simple language and analogies that they can relate to should be used.

    For example, let’s say the concept of ‘API’ is to be explained. One could start by explaining that an API is a set of rules and protocols that allows software programs to communicate with each other.

    They could then use the example of ordering food from a restaurant’s website. The restaurant’s website has a menu, and for the customer to place an order, the website needs to talk to the restaurant’s kitchen. Only then can it confirm the availability of the menu items and pricing, and place the order. The website communicates with the kitchen systems through an API. Similarly, other programs use APIs to communicate with each other.

    3: Do you have any technical certifications?

    Certifications to look for in the sample answer: C, C++, Java, Python, MySQL, etc.

    Question 4: What is the difference between a stack and a queue?

    Expected answer: A stack and a queue are both data structures. Yet, they serve different purposes and have different characteristics.

    A stack is a Last-In, First-Out (LIFO) data structure. This means that the last element added to the stack is the first one to be removed.

    A queue is a First-In, First-Out (FIFO) data structure. This means that the first element added to the queue is the first one to be removed.

    One can change the order of questions or the intensity of testing for programming expertise based on the experience that a candidate has.


    Programming Interview Questions

    One can start with simple questions that assess the level of experience and expertise that candidates have. Some may have completed a coding boot camp or an introductory course, may have written basic programs, and may understand basic programming concepts, while others have a few years of experience.

    1:What is object-oriented language?

    Object-oriented languages use the concept of ‘objects,’ which are entities that encapsulate data and behavior. Here, the programs use objects that interact with each other through methods, which are functions associated with a class or an object.

    Java, C++, C#, Python, and Ruby are some examples of object-oriented languages.

    2: How can static and dynamic typed languages be differentiated?

    Expected Answer: In statically typed languages, the variable type is explicitly declared by the developer before it is used. The type of a variable determines the kind of data it can store, such as an integer, string, or boolean. Once a variable type is declared, it cannot be reassigned to a different type. Examples of static typed languages include Java, C++, and C#.

    Dynamically typed languages do not require the developer to explicitly declare the type. The type of a variable is determined at runtime by the value it is assigned. This means that the same variable can be reassigned to different types of data at different times in the program. Examples of dynamically typed languages include Python, Ruby, and JavaScript.

    The main difference between the two is that static typed language provides more compile-time type-checking. It makes it easy to catch errors earlier in the development process. Dynamically typed languages are more flexible and easier to write or read, but they can lead to more runtime errors.

    3: What programming languages can you work with?

    Programming languages like Python, Java, JavaScript, C, C++, C#, SQL, PHP, Ruby, Kotlin, MATLAB, Swift, Rust, Dart, and Scala.

    4: What are the exceptions and errors in Java?

    In Java, an exception is an event that occurs during the program execution and disrupts the normal flow of instructions.

    An error is a more serious problem that indicates an issue with the program itself. It is not an exceptional condition that can be handled.

    In Java, exceptions are represented by classes that extend the Java.lang.Exception class, while errors are represented by classes that extend the Java.lang.Error class.

    5: What is the DRY principle?

    The DRY principle stands for ‘Don’t Repeat Yourself.’ It aims to reduce redundant code and improve the maintainability of a program. The idea of this principle is that every piece of knowledge in a system should have a single, unambiguous representation. It encourages developers to create reusable code and avoid duplicating logic or data.


    6: Define data abstraction in Java.

    Data abstraction in Java is a mechanism for hiding the implementation details of a class. It exposes only the necessary information to users. It is a fundamental concept in object-oriented programming.

    For example, a class that represents a bank account can be defined as an abstract class with methods like deposit and withdrawal. The implementation of these methods can be different for different types of bank accounts (e.g., savings and checking). The user of the class can interact with the class by only knowing the methods and not how they are implemented.

    7: How can the first non-repeated character in a word be found?

    One common approach is to use a data structure, such as a hash map. It keeps track of the frequency of each character in a word.

    Here’s an example of the implementation of this approach in Java:

    Public static Character firstNonRepeatedCharacter(String word) {

        HashMap<Character, Integer> charCount = new HashMap<Character, Integer>();

        // Store the count of each character in the HashMap

        for (int i = 0; i < word.length(); i++) {

            char c = word.charAt(i);

            if (charCount.containsKey(c)) {

                charCount.put(c, charCount.get(c) + 1);

            } else {

                charCount.put(c, 1);



        // Iterate through the word and return the first nonrepeated character

        for (int i = 0; i < word.length(); i++) {

            char c = word.charAt(i);

            if (charCount.get(c) == 1) {

                return c;



        // If no nonrepeated character is found, return null

        return null;


    8: What is a garbage collector in Java? Can you explain a few garbage collectors?

    Garbage collectors are used to remove objects that are no longer in use. An object is declared non-usable if it cannot be accessed by a thread, and it is removed to free up memory space.

    Serial Garbage Collector (SGC): It is the simplest form of garbage collector. It performs the process of removing objects in a single thread and is suitable for small- and medium-sized applications.

    Parallel Garbage Collector (PGC): It uses multiple threads to remove unused objects from an application. It is suitable for large-sized applications that require a large number of unused objects to be removed.

    Concurrent Mark and Sweep Garbage Collector (CMSGC): It reduces the time spent on the garbage collection process by working concurrently with the application.

    9: Is it possible to synchronize two Java processes?

    Yes, two Java processes can be synchronized using the built-in synchronization mechanisms in Java.

    One way to synchronize two Java processes is by using the synchronized keyword. This keyword synchronizes access to a method or a block of code and ensures that only one thread can execute the synchronized code at a time.

    Another way is to use the lock interface and its implementing classes, such as ReentrantLock. This interface provides more fine-grained control over synchronization.

    Interview Point Sheets

    It is tiring and inefficient to come up with different questions for each candidate every time. It is even more difficult to compare each candidate’s answers to different questions.

    An interview point sheet can be a useful tool for interviewers, as it helps ensure that all candidates are evaluated in a consistent/fair manner.

    Listed here are a few examples of what to include in the interview point sheet:

    • Technical skills: Programming languages, frameworks or tools that the candidate should know

    • Problem-solving skills: Questions or scenarios designed to test the candidate’s ability to think critically

    • Experience: Questions or tasks designed to assess the candidate’s prior experience in a given field or role

    One Last Tip

    Change the questions from time to time to make sure candidates are not getting answers by using various hacks to do better. Also, continuously review or update the questionnaire to make sure it is relevant and effective.

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