Impiger Technologies Junior .NET Developer Interview Questions and Answers

Q1. Explain Abstraction and Encapsulation
Ans. 
Abstraction focuses on hiding implementation details, while encapsulation bundles data and methods into a single unit.
• Abstraction allows us to focus on the essential features of an object while hiding unnecessary details.

• Encapsulation helps in data hiding by restricting access to certain components of an object.

• Abstraction is achieved through abstract classes and interfaces in Java.

• Encapsulation is implemented using ac...read more
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Q2. Explain the use of Final keyword
Ans. 
Final keyword is used in Java to declare constants, prevent method overriding, and prevent class inheritance.
• Used to declare constants - value cannot be changed once assigned

• Prevents method overriding - method cannot be overridden in child classes

• Prevents class inheritance - class cannot be extended
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Q3. Difference between == operator and equals method
Ans. 
The == operator compares memory addresses, while the equals method compares the actual content of objects.
• The == operator checks if two object references point to the same memory address.

• The equals method checks if two objects have the same content.

• Example: String str1 = new String("hello"); String str2 = new String("hello"); str1 == str2 will return false, but str1.equals(str2) will return true.
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Q4. Explain about Hash Table
Ans. 
Hash table is a data structure that stores key-value pairs and allows for fast retrieval of values based on keys.
• Hash table uses a hash function to map keys to indexes in an array.

• It provides constant time complexity O(1) for insertion, deletion, and retrieval operations.

• Collisions can occur when two keys hash to the same index, which can be resolved using techniques like chaining or open addressing.
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Q5. What is Synchronized keyword
Ans. 
Synchronized keyword is used in Java to control access to shared resources by multiple threads.
• Synchronized keyword is used to create a synchronized block of code, ensuring only one thread can access it at a time.

• It can be applied to methods or code blocks to prevent concurrent access by multiple threads.

• Example: synchronized void myMethod() { // synchronized code block }
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Q6. What is the use of volatile keyword
Ans. 
The volatile keyword in Java is used to indicate that a variable's value will be modified by different threads.
• Ensures visibility of changes to variables across threads

• Prevents compiler optimizations that could reorder code and affect variable values

• Useful for variables accessed by multiple threads without synchronization

• Example: volatile int count = 0;
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Q7. What are checked and unchecked exceptions
Ans. 
Checked exceptions are checked at compile time, while unchecked exceptions are not.
• Checked exceptions must be either caught or declared in the method signature using 'throws' keyword

• Unchecked exceptions do not need to be caught or declared

• Examples of checked exceptions: IOException, SQLException

• Examples of unchecked exceptions: NullPointerException, ArrayIndexOutOfBoundsException
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Q8. Difference between Interface and Abstract class
Ans. 
Interface is a blueprint of a class with only abstract methods, while abstract class can have both abstract and concrete methods.
• Interface cannot have method implementations, while abstract class can have both abstract and concrete methods.

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

• Interfaces are used to achieve multiple inheritance in Java, while abstract classes are used to provi...read more
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Q9. Explain Dead lock in multi threading
Ans. 
Deadlock in multithreading occurs when two or more threads are waiting for each other to release resources, resulting in a standstill.
• Deadlock happens when two or more threads are blocked forever, waiting for each other to release resources.

• Four conditions must hold for deadlock to occur: mutual exclusion, hold and wait, no preemption, and circular wait.

• Example: Thread 1 holds resource A and waits for resource B, while...read more
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Q10. How to achieve thread safety in java
Ans. 
Thread safety in Java can be achieved by using synchronization, locks, volatile keyword, and thread-safe data structures.
• Use synchronized keyword to create synchronized blocks or methods

• Use locks from java.util.concurrent.locks package like ReentrantLock

• Use volatile keyword to ensure visibility of changes across threads

• Use thread-safe data structures like ConcurrentHashMap, CopyOnWriteArrayList
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Q11. Difference between PUT and POST method
Ans. 
PUT is used to update or replace an existing resource, while POST is used to create a new resource.
• PUT is idempotent, meaning multiple identical requests will have the same effect as a single request.

• POST is not idempotent, meaning multiple identical requests may have different effects.

• PUT is used to update an existing resource at a specific URI.

• POST is used to create a new resource under a specific URI.

• PUT requests ar...read more
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Q12. What are Spring Actuator
Ans. 
Spring Actuator is a set of production-ready features to help monitor and manage your application.
• Provides endpoints to monitor application health, metrics, and other useful information

• Can be used to check the status of the application, gather metrics, and even perform custom actions

• Helps in troubleshooting and monitoring the application in production environment
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Q13. How to deploy a spring boot application
Ans. 
Spring Boot applications can be deployed using various methods such as embedded servers, Docker containers, and cloud platforms.
• Deploying as a standalone JAR file using embedded servers like Tomcat or Jetty

• Building a Docker image and running the application in a container

• Deploying to cloud platforms like AWS, Azure, or Google Cloud Platform

• Using CI/CD pipelines for automated deployment
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Q14. Write a program with Java 8 to filter the employees based on salary greater than 10,000 from a list of Employee objects.
Ans. 
Program to filter employees with salary > 10,000 using Java 8.
• Use Java 8 Stream API to filter employees based on salary.

• Create a Predicate to check if salary is greater than 10,000.

• Use filter() method to apply the Predicate on the list of Employee objects.
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Q15. How to rollback a transaction in spring boot
Ans. 
To rollback a transaction in Spring Boot, use @Transactional annotation and throw an exception
• Use @Transactional annotation on the method where the transaction needs to be rolled back

• Throw an exception within the method to trigger the rollback process

• Spring will automatically rollback the transaction when an exception is thrown
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Q16. Explain Dependency Injection in spring boot
Ans. 
Dependency Injection is a design pattern in Spring Boot where the dependencies of a class are injected from the outside.
• In Spring Boot, Dependency Injection is achieved through inversion of control, where the control of creating and managing objects is given to the Spring framework.

• Dependencies can be injected into a class using constructor injection, setter injection, or field injection.

• By using Dependency Injection, ...read more
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Q17. Different ways of Dependency Injection
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Dependency Injection is a design pattern where the dependencies of an object are provided externally rather than created within the object itself.
• Constructor Injection: Dependencies are provided through the class constructor.

• Setter Injection: Dependencies are set through setter methods.

• Interface Injection: Dependencies are injected through an interface.

• Spring Framework: Uses annotations like @Autowired for Dependency I
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Q18. Explain Security management, how to enable security for APIs.
Ans. 
Security management involves implementing measures to protect APIs from unauthorized access and ensure data integrity.
• Implement authentication mechanisms such as OAuth or API keys to control access to APIs

• Use encryption to secure data transmission between clients and APIs

• Implement rate limiting to prevent abuse and protect against denial of service attacks

• Regularly update and patch API security vulnerabilities to stay ...read more
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Q19. Explain JWT Tokens
Ans. 
JWT Tokens are a type of token used for authentication and authorization in web applications.
• JWT stands for JSON Web Token

• JWT tokens are compact, URL-safe tokens that can be easily transmitted between parties

• JWT tokens consist of three parts: header, payload, and signature

• JWT tokens are often used in stateless authentication systems

• Example: eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiIxMjM0NTY3ODkwIiwibmFtZSI6IkpvaG...read more
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Q20. How to write a test case for a private method
Ans. 
Use reflection to access and test private methods
• Use reflection to access the private method in the test case

• Set the method accessible using setAccessible(true)

• Invoke the method with the necessary parameters and assert the expected result
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Q21. Stages in Jenkins
Ans. 
Stages in Jenkins are the different steps in a Jenkins pipeline that define the actions to be executed.
• Stages help break down the pipeline into smaller, manageable sections

• Each stage can have multiple steps to be executed

• Stages can be sequential or parallel

• Common stages include build, test, deploy, and notify
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Q22. Write the singleton design pattern
Ans. 
Singleton design pattern ensures a class has only one instance and provides a global point of access to it.
• Create a private static instance of the class.

• Provide a public static method to access the instance.

• Ensure the constructor is private to prevent instantiation from outside the class.
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Q23. What is memory leaks in java
Ans. 
Memory leaks in Java occur when objects are no longer being used but are still held in memory, leading to inefficient memory usage.
• Memory leaks can occur when objects are not properly dereferenced or garbage collected.

• Common causes of memory leaks include circular references, static references, and unclosed resources.

• Examples of memory leaks include not closing database connections or file streams after use.
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Q24. Difference between String and String builder
Ans. 
String is immutable, while StringBuilder is mutable and more efficient for concatenating strings.
• String is immutable, meaning once created, it cannot be changed. StringBuilder is mutable and allows for modifications.

• String concatenation in Java creates a new String object each time, while StringBuilder modifies the existing object.

• StringBuilder is more efficient for concatenating multiple strings as it does not create ...read more
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Q25. Explain Garbage Collection in java
Ans. 
Garbage collection in Java is the process of automatically reclaiming memory that is no longer in use by the program.
• Garbage collection is performed by the JVM to free up memory occupied by objects that are no longer referenced by the program.

• It helps in preventing memory leaks and ensures efficient memory management.

• Java provides automatic garbage collection, so developers do not have to manually free up memory.

• Exampl...read more
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Q26. Difference between Array and ArrayList.
Ans. 
Array is a fixed-size data structure while ArrayList is a dynamic-size data structure in Java.
• Array is a fixed-size collection of elements of the same data type.

• ArrayList is a resizable collection that can store elements of any data type.

• Arrays require a specified size at the time of declaration, while ArrayList can grow dynamically.

• Arrays use square brackets [] for declaration, while ArrayList is a class in Java's col...read more
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Q27. Design patterns used
Ans. 
Various design patterns like Singleton, Factory, Observer, etc. are used to solve common problems in software development.
• Singleton pattern ensures a class has only one instance and provides a global point of access to it.

• Factory pattern creates objects without specifying the exact class of object that will be created.

• Observer pattern defines a one-to-many dependency between objects so that when one object changes stat...read more
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Q28. What is Rest Services
Ans. 
Rest Services are a type of web service that allows communication between different systems over HTTP using standard methods like GET, POST, PUT, DELETE.
• Rest Services are stateless, meaning each request from a client to the server must contain all the information necessary to understand the request.

• They use standard HTTP methods like GET, POST, PUT, DELETE to perform CRUD operations on resources.

• Rest Services typically...read more
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Q1. Tech questions on dot net
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Q1. To check your knowledge and communication skills
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Q1. They are not even proceeding on time with the client interview . I have to quit the process because they already took 1 week for client interview round
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Q1. Basic discussion.
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2 DSA question was asked

40 questions in 20 minutes

Q1. Stones games 2 leetcode
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Q2. Permutations of array
Ans. 
Generate all possible permutations of an array of strings
• Use recursion to generate permutations

• Swap elements to create different permutations

• Base case: when array size is 1, return array as permutation
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Q1. Project discussion
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Q1. What is normalization
Ans. 
Normalization is the process of organizing data in a database to reduce redundancy and improve data integrity.
• Normalization helps in minimizing data redundancy by dividing the database into multiple tables.

• It ensures data integrity by avoiding update anomalies.

• Normalization is achieved through a series of rules called normal forms, such as 1NF, 2NF, 3NF, etc.

• Example: In a database, instead of storing customer details i...read more
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Q2. What is reflection
Ans. 
Reflection is the ability of a program to examine and modify its own structure and behavior at runtime.
• Allows accessing metadata of types and members at runtime

• Enables dynamic instantiation of objects

• Facilitates invoking methods dynamically
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30min Pseudo Code,Ratio and Proportion

1 hour Array,HashMap

Q1. Write a program a string is Anagram or not
Ans. 
Program to check if a string is an Anagram or not
• Create a function that takes in two strings as input

• Sort the characters in both strings and compare if they are equal

• Return true if they are anagrams, false otherwise
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Q2. How to connect mongodb with database
Ans. 
To connect MongoDB with a database, you need to use the MongoDB URI and a MongoDB client library.
• Use the MongoDB URI to specify the connection details such as host, port, username, password, and database name

• Install a MongoDB client library like Mongoose for Node.js or pymongo for Python

• Use the client library to establish a connection to the MongoDB database and perform CRUD operations
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Q3. What is event listener
Ans. 
An event listener is a function that waits for a specific event to occur and then triggers a response.
• Event listeners are commonly used in web development to handle user interactions like clicks, keypresses, etc.

• They are attached to specific elements and listen for events to occur on those elements.

• Once the event occurs, the listener executes a callback function to respond to the event.

• Example: Adding a click event lis...read more
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Q4. What is polymorphism
Ans. 
Polymorphism is the ability of a function or method to behave differently based on the object it is acting upon.
• Polymorphism allows objects of different classes to be treated as objects of a common superclass.

• There are two types of polymorphism: compile-time (method overloading) and runtime (method overriding).

• Example: Inheritance in object-oriented programming languages like Java allows for polymorphism.
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Q1. How to reverse a string without using extra space
Ans. 
Use two pointers to swap characters in place
• Initialize two pointers, one at the beginning of the string and one at the end

• Swap characters at the two pointers and move them towards each other until they meet or cross

• Repeat the process until the entire string is reversed
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Q2. Find a number that not present in array in O(N) time complexity array contain only 0 to n numbers
Ans. 
Use bitwise XOR operation to find the missing number in O(N) time complexity.
• Iterate through the array and XOR all the elements with their indices and the array length.

• The missing number will be the result of XORing all the elements with their indices and the array length.
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Q3. Why should you join this company
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Q4. How many interview have you give previously and why you get rejected
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60mintues DSA level coding exam

Q1. Explain React life cycle
Ans. 
React life cycle refers to the series of methods that are invoked in the process of creating, updating, and destroying components.
• Mounting phase: constructor, render, componentDidMount

• Updating phase: render, componentDidUpdate

• Unmounting phase: componentWillUnmount
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Q2. Design a online calculator app
Ans. 
An online calculator app that allows users to perform basic arithmetic operations.
• Include buttons for numbers 0-9 and operators like +, -, *, /

• Implement functionality for clearing input, calculating result, and displaying history

• Consider adding advanced features like memory functions or scientific calculator mode
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