200+ Junior Software Developer Interview Questions and Answers

The player who picks the last coin loses the game.

• The game starts with n coins.

• Each player can pick 1 to 5 coins in one turn.

• The player who picks the last coin loses the game.

• Determine if the given n coins will result in a win or loss for the starting player.

Answering questions about golang, job switch, salary expectations, and location comfort.

• Golang is a programming language developed by Google, known for its simplicity and efficiency.

• I have used golang in my previous job to develop a microservices architecture for a web application.

• I am looking to switch jobs to gain new experiences, challenges, and opportunities for growth.

• My salary expectation is based on my skills, experience, and market standards.

• I am comfortable working i...read more

b) x is four bit integer.

• The statement 'int x:4;' indicates that x is a four bit integer.

• A four bit integer can have values ranging from 0 to 15.

• The colon followed by the number 4 specifies the number of bits allocated for x.

A lint is an analyzing tool used to identify and report coding errors, bugs, and stylistic issues in software code.

• Lint is commonly used in programming languages like C, C++, Java, and Python.

• It helps developers catch potential bugs and improve code quality.

• Lint tools can detect issues such as unused variables, missing semicolons, and inconsistent indentation.

• Examples of popular linters include ESLint for JavaScript and Pylint for Python.

Reverse a linked list using recursion, handling all corner cases

• Create a recursive function that takes the head of the linked list as input

• Base case: if the head is null or the list contains only one node, return the head

• Recursively call the function with the next node as input and set its next pointer to the current node

• Set the current node's next pointer to null and return the new head

Checked and Unchecked Exceptions are types of exceptions in Java. Checked exceptions are checked at compile-time while unchecked exceptions are not.

• Checked exceptions are those which are checked at compile-time and must be handled by the programmer using try-catch or throws keyword.

• Examples of checked exceptions include IOException, SQLException, ClassNotFoundException.

• Unchecked exceptions are those which are not checked at compile-time and can occur at runtime.

• Examples of un...read more

Yes, we can use super and this in a single constructor.

• Using 'super' in a constructor calls the parent class constructor.

• Using 'this' in a constructor calls another constructor in the same class.

• We can use both 'super' and 'this' in the same constructor to call both parent and same class constructors.

• Example: public MyClass(int x) { this(x, 0); super(); }

Binary search can be used to find the number in a sorted array in log(n) time.

• Implement binary search algorithm to find the number in the sorted array.

• If the number is not found, return the index where it should be inserted.

• Time complexity of binary search is O(log n).

Interfaces define a contract for classes to implement, while abstract classes can have both abstract and concrete methods.

• Interfaces can only have abstract methods and constants, while abstract classes can have both abstract and concrete methods.

• A class can implement multiple interfaces but can only inherit from one abstract class.

• Interfaces are used for achieving multiple inheritance in Java, while abstract classes are used to define a common behavior for subclasses.

• Interfac...read more

Yes, protected members are inherited in subclasses in hierarchy.

• Protected members are accessible within the class and its subclasses.

• They are not accessible outside the class hierarchy.

• Subclasses can access protected members of their parent class.

• Example: class A has a protected member x, class B extends A can access x.

• Example: class C extends B can also access x.

The super class of Exception is Throwable.

• Throwable is the root class of all exceptions in Java.

• It has two direct subclasses: Exception and Error.

• Exceptions are used for recoverable errors while Errors are used for unrecoverable errors.

• All exceptions and errors inherit from Throwable.

• Throwable provides methods like getMessage() and printStackTrace() to handle exceptions.

Constructor creates and initializes an object, while method performs an action on an object.

• Constructor has the same name as the class and is called when an object is created

• Method has a name that describes the action it performs on an object

• Constructor initializes the object's state, while method changes the object's state

• Constructor doesn't have a return type, while method can have a return type

• Example: public class Car { public Car() { ... } public void start() { ... } }

• In...read more

A stored procedure is a precompiled set of SQL statements that can be called by name, while a function returns a value.

• Stored procedures are used to perform a specific task, such as inserting or updating data in a database.

• Functions return a value, while stored procedures do not necessarily return a value.

• Stored procedures can be called from within other SQL statements, while functions cannot.

• Stored procedures can have input and output parameters, while functions can only hav...read more

Binary Search Tree is a data structure where each node has at most two children, with left child smaller and right child larger. Time complexity is O(log n) for search, insert, and delete operations.

• Nodes have at most two children - left child is smaller, right child is larger

• Search, insert, and delete operations have time complexity of O(log n)

• Example: In a BST, if we search for a value, we can eliminate half of the remaining nodes at each step

Java, Python, PHP, DBMS, and .NET are all programming languages or technologies used in software development.

• Java is an object-oriented programming language used for developing desktop, web, and mobile applications.

• Python is a high-level programming language used for web development, data analysis, artificial intelligence, and scientific computing.

• PHP is a server-side scripting language used for web development and creating dynamic web pages.

• DBMS stands for Database Managemen...read more

Data structures are essential for efficient storage and retrieval of data.

• Data structures allow for faster access and manipulation of data.

• They help in organizing and managing large amounts of data.

• Examples include arrays, linked lists, trees, and graphs.

• Without data structures, algorithms would be less efficient and more complex.

• Data structures are used in various fields such as computer science, finance, and engineering.

Count the number of 0's in a sorted array of 0's and 1's.

• Iterative solution: Traverse the array and count the number of 0's.

• Recursive solution: Divide the array into two halves and recursively count the number of 0's in each half.

• Binary search can also be used to find the first occurrence of 0 and then count the number of 0's after that index.

Function to add two numbers represented by linked lists and return the sum list.

• Traverse both linked lists and add corresponding nodes, keeping track of carry

• Create a new linked list to store the sum

• Handle cases where linked lists are of different lengths

• Handle cases where the sum has an extra digit due to carry

• Return the sum linked list

Array is a fixed-size data structure while linked list is a dynamic data structure. ArrayList and LinkedList are implementations of List interface in Java.

• Array is a contiguous block of memory with fixed size, while linked list is a collection of nodes where each node points to the next node.

• ArrayList in Java is implemented using an array, which can dynamically resize itself. LinkedList is implemented using nodes with references to the next and previous nodes.

• Arrays are faste...read more

SQL joins are used to combine data from two or more tables based on a related column between them.

• Inner join returns only the matching rows from both tables

• Left join returns all rows from the left table and matching rows from the right table

• Right join returns all rows from the right table and matching rows from the left table

• Full outer join returns all rows from both tables

• Cross join returns the Cartesian product of both tables

Java is a high-level, object-oriented programming language used for developing applications and software.

• Java was developed by James Gosling at Sun Microsystems in the mid-1990s.

• It was originally called Oak and was designed for use in consumer electronics.

• Java syntax is similar to C++ and C#.

• Java code is compiled into bytecode that can run on any platform with a Java Virtual Machine (JVM).

A list of technical questions for a Junior Software Developer position.

• Super is a keyword in Java used to refer to the parent class.

• Java is platform independent due to its bytecode being able to run on any platform with a JVM.

• Multiple Inheritance is the ability for a class to inherit from multiple parent classes.

• The diamond problem occurs when a class inherits from two classes that have a common ancestor, causing ambiguity.

• Normalization is the process of organizing data in a ...read more

Programming language is a set of instructions used to communicate with computers. To become a good programmer, one needs to practice and learn continuously.

• Choose a language and stick to it

• Practice coding regularly

• Read and understand code written by others

• Learn data structures and algorithms

• Stay updated with new technologies and trends

JOIN is used in MySQL to combine data from two or more tables based on a related column between them.

• JOIN is used to retrieve data from multiple tables in a single query

• It is used to combine rows from two or more tables based on a related column between them

• Types of JOIN include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN

• Example: SELECT * FROM table1 JOIN table2 ON table1.column = table2.column

JavaScript basics, React concepts, array manipulation

• let, var, and const are used to declare variables in JavaScript with different scoping rules

• Single page application is a web application that dynamically updates the content without reloading the page

• Virtual DOM is a lightweight copy of the actual DOM used by React to improve performance

• To separate even and odd values in an array, use filter() method with a condition

• To remove duplicates in an array, use Set() or filter() me...read more

Given a number n, find the number just greater than n using same digits as that of n

• Convert the number to a string and sort the digits in ascending order

• Starting from the rightmost digit, find the first digit that is smaller than the digit to its right

• Swap this digit with the smallest digit to its right that is greater than it

• Sort the digits to the right of the swapped digit in ascending order

• Concatenate the digits to get the next greater number

Program to form a string with first character of all words in a given string.

• Split the string into an array of words

• Iterate through the array and extract the first character of each word

• Join the extracted characters to form the final string

Software engineering offers numerous advantages in terms of efficiency, scalability, and maintainability.

• Efficiency: Software engineering practices help in optimizing code and improving performance.

• Scalability: Proper software engineering enables the development of scalable systems that can handle increasing workloads.

• Maintainability: Well-structured software is easier to maintain, debug, and enhance over time.

• Reusability: Software engineering promotes the reuse of code compo...read more

A mixin is a way to add functionality to a class without using inheritance. Ruby does not support multiple inheritance due to potential conflicts.

• Mixins in Ruby are achieved using modules, which can be included in classes to add methods and attributes.

• Ruby does not support multiple inheritance because it can lead to the diamond problem, where conflicting methods from different parent classes cause ambiguity.

• Instead of multiple inheritance, Ruby encourages the use of mixins an...read more

To stop async code based on specification condition, use cancellation tokens.

• Use CancellationTokenSource to create a cancellation token

• Pass the cancellation token to the async method

• Check the cancellation token in the async method using ThrowIfCancellationRequested()

• Cancel the token when the specification condition is met

To maximize the area of a container formed by two parallel bars, use the two-pointer approach in O(n) time complexity.

• Use the two-pointer approach to iterate from both ends towards the center of the array.

• Calculate the area formed by the two bars at each step and update the maximum area found so far.

• Move the pointer with the smaller height towards the center to potentially find a larger area.

• Repeat the process until the pointers meet in the middle of the array.

You can use an ArrayList in Java to dynamically change the size of the array without creating a new array.

• Use ArrayList instead of String[] to store strings in a dynamic array.

• You can add or remove elements from the ArrayList as needed without creating a new array.

• Example: ArrayList strings = new ArrayList(); strings.add("Hello"); strings.add("World");

Yes, I am familiar with SQL and can demonstrate how to implement the structure.

• SQL is a standard language for storing, manipulating, and retrieving data in databases.

• To implement the structure in SQL, you would use CREATE TABLE statement to define the structure of a table.

• For example, CREATE TABLE Students (id INT, name VARCHAR(50), age INT); would create a table named Students with columns id, name, and age.

Use GROUP BY and HAVING clause to find duplicate rows in a table without using DISTINCT.

• Use GROUP BY to group rows with the same values together

• Use HAVING clause to filter out groups with only one row

• Select columns to display duplicate rows

Exception handling in C++ and Java

• C++ uses try-catch blocks to handle exceptions

• Java uses try-catch-finally blocks to handle exceptions

• Both languages have a hierarchy of exception classes

• C++ has the throw keyword to throw an exception

• Java has the throw keyword to throw an exception

• C++ allows for custom exception classes to be created

• Java has predefined exception classes like NullPointerException

It is not possible to accurately estimate the number of lines of code that can be written in one day.

• The number of lines of code that can be written in a day depends on various factors such as complexity, requirements, and experience.

• It is important to focus on writing clean and efficient code rather than just aiming for a specific number of lines.

• Collaboration and teamwork can also impact the productivity and speed of coding.

• Providing an estimate without analyzing the specif...read more

Redux is a predictable state container for JavaScript apps, commonly used with React to manage application state.

• Redux helps in managing the state of the application in a predictable way.

• It provides a single source of truth for the state of the application.

• Redux allows for easier debugging and testing of the application.

• Actions are dispatched to update the state in Redux.

• Reducers specify how the state changes in response to actions.

Count the number of perfect subarrays in an array where odd values are at odd positions and even values are at even positions.

• Iterate through the array and keep track of the count of odd and even numbers encountered so far.

• If the count of odd and even numbers at the current index matches the index itself, increment the count of perfect subarrays.

• Example: For array [2, 1, 3, 4], there are 3 perfect subarrays: [2, 1], [1, 3, 4], [3, 4].

Callbacks are methods that are called at certain points in an object's lifecycle. Destroy permanently deletes a record, while delete marks it as deleted.

• Validation callbacks are methods that are called before or after validations on an object. They are used to ensure data integrity.

• Destroy method permanently deletes a record from the database, including associated records. It does not trigger callbacks or validations.

• Delete method marks a record as deleted in the database, bu...read more

Hashing is a technique to map data to a fixed-size value. To retain unique elements in a collection, use a hash set.

• Create a hash set to store unique elements

• Iterate through the collection and add each element to the hash set

• If an element already exists in the hash set, skip adding it to retain only unique elements

In Spring Boot, PUT is used to update an existing resource, while POST is used to create a new resource. Input validation can be done using annotations like @Valid.

• Use PUT method to update an existing resource

• Use POST method to create a new resource

• Validate input using annotations like @Valid in Spring Boot

API testing is the process of testing APIs to ensure they meet functionality, reliability, performance, and security requirements.

• API testing involves testing the functionality, reliability, performance, and security of APIs.

• It focuses on verifying that the API works as expected, returns correct data, and handles errors properly.

• API testing can be done manually or using automated tools like Postman or SoapUI.

• Examples of API testing include testing endpoints, data validation, ...read more

Java is a statically typed, object-oriented programming language, while Python is dynamically typed and focuses on simplicity and readability.

• Java is statically typed, meaning variables must be declared with a specific data type, while Python is dynamically typed.

• Java is more verbose and requires more code to accomplish tasks compared to Python.

• Python emphasizes simplicity and readability, making it easier for beginners to learn and use.

• Java is commonly used for building ente...read more

Many to many vs has and belongs to many association, and explanation of polymorphic association.

• Many to many association involves a join table to connect two models with a many-to-many relationship.

• Has and belongs to many association is a simpler version of many to many, where the join table is hidden.

• Polymorphic association allows a model to belong to more than one other model, using a single association.

• Example: Many to many - Students and Courses, HABTM - Users and Roles, ...read more

Inheritance is a concept in object-oriented programming where a class inherits properties and behaviors from another class.

• Inheritance allows for code reusability and promotes a hierarchical relationship between classes.

• Example: Class B inherits from Class A, gaining access to its attributes and methods.

• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• Example: A method that can take an object of a parent class as an argument can...read more

Input and output functions in C language are used to interact with the user and the external environment.

• Input functions in C include scanf() for reading input from the user and getchar() for reading a single character.

• Output functions in C include printf() for displaying output to the user and putchar() for displaying a single character.

• File input and output functions in C include fopen(), fclose(), fread(), and fwrite() for reading from and writing to files.

Client-side validation is the process of validating user input on the client-side before submitting it to the server.

• It is performed using JavaScript or HTML5 attributes.

• It helps to reduce server load and improve user experience.

• It can be easily bypassed, so server-side validation is also necessary.

• Examples include checking for required fields, email format, and password strength.