Sonar Technologies 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
Ans. 
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. What programming languages do you know?
Ans. 
I am proficient in Java, Python, and SQL.
• Java

• Python

• SQL
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Q2. Why should we hire you
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Q3. Explain database partitioning
Ans. 
Database partitioning is the process of splitting a large database into smaller, more manageable parts.
• Improves performance by distributing data across multiple servers or disks

• Helps with scalability and maintenance

• Types include horizontal partitioning (rows) and vertical partitioning (columns)

• Example: Partitioning a customer database by region to improve query performance
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Q4. Describe your production deployment process
Ans. 
Our production deployment process involves thorough testing, version control, and automated deployment.
• Thorough testing of the code before deployment

• Version control to track changes and rollback if necessary

• Automated deployment using tools like Jenkins or Ansible
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Q5. Tell me about yourself
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Q6. What are your salary expectations
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Q7. What are your hobbies
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Q8. What is system design
Ans. 
System design is the process of defining the architecture, components, modules, interfaces, and data for a system to satisfy specified requirements.
• System design involves creating a detailed blueprint of how the system will be structured and function.

• It includes defining the system architecture, components, modules, interfaces, and data.

• System design ensures that the system meets the specified requirements and function...read more
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Q9. What is testing and debugging
Ans. 
Testing is the process of evaluating a system or application to find defects or bugs, while debugging is the process of identifying and fixing those defects.
• Testing involves executing the system or application to identify defects or bugs.

• Debugging involves identifying and fixing the defects found during testing.

• Testing is done by testers, while debugging is usually done by developers.

• Examples of testing include unit te...read more
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Q10. Explain data structure and algorithm
Ans. 
Data structure is a way of organizing and storing data in a computer so that it can be accessed and used efficiently. Algorithms are step-by-step procedures for solving problems.
• Data structure refers to the way data is organized and stored in a computer system.

• Algorithms are step-by-step procedures for solving problems or performing tasks.

• Examples of data structures include arrays, linked lists, trees, and graphs.

• Examp...read more
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Q11. Describe the concept of a binary search algorithm and its time complexity
Ans. 
Binary search algorithm is a divide and conquer algorithm that searches for a target value within a sorted array.
• Binary search compares the target value to the middle element of the array and eliminates half of the remaining elements based on the comparison.

• Time complexity of binary search is O(log n) where n is the number of elements in the array.

• Example: Searching for the value 7 in the sorted array [1, 3, 5, 7, 9, 1
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Q12. What is horizontal scaling and how does it differ from vertical scaling?
Ans. 
Horizontal scaling involves adding more machines to distribute load, while vertical scaling involves increasing the power of existing machines.
• Horizontal scaling adds more machines to handle increased load

• Vertical scaling increases the power of existing machines

• Horizontal scaling is more cost-effective and easier to implement

• Examples of horizontal scaling include adding more servers to a cluster

• Examples of vertical sca
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Q13. How does caching work in web development?
Ans. 
Caching in web development involves storing copies of files or data in a temporary location to reduce load times and improve performance.
• Caching helps reduce server load by serving cached content instead of generating it from scratch.

• Common types of caching include browser caching, server-side caching, and database caching.

• Examples of caching techniques include using HTTP headers to control browser caching, implementin...read more
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Q14. What are the different programming languages used in web development?
Ans. 
Various programming languages are used in web development, each with its own strengths and purposes.
• HTML

• CSS

• JavaScript

• Python

• Ruby

• PHP
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Q15. Explain the concept of a linked list and its advantage over an array
Ans. 
A linked list is a data structure where each element points to the next element, offering dynamic size and efficient insertion/deletion.
• Linked list elements are not stored in contiguous memory locations like arrays, allowing for dynamic size allocation.

• Insertion and deletion operations are faster in linked lists compared to arrays as elements can be easily rearranged by changing pointers.

• Linked lists are more memory ef...read more
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Be prepared to give specific examples from your experience, education, or skills that are relevant to the job and organization

Comprehensive technique to judge the suitability of an individual and his appropriateness for admission, scholarship, job, etc.

A way for employers to assess a candidate's abilities through a variety of different testing formats

Q1. Basics of SQL, PL/SQL, cursors and their types, Oracle Finance module of Account Payables, Account Receivables, General Ledger, Order management; their flow, concurrent program name that transfer to GL mod...read more
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Q1. The manager shared the success growth of Equifax
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Q2. What are mutating tables?
Ans. 
Mutating tables refer to tables that are being modified by an ongoing transaction.
• Mutating tables occur when a trigger or a stored procedure tries to read or modify a table that is already being modified by the same transaction.

• This can lead to errors like ORA-04091: table is mutating, trigger/function may not see it.

• To avoid mutating table errors, you can use autonomous transactions, compound triggers, or row-level tr...read more
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Q1. Salary discussion, work location
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Object Detection on a subset of COCO dataset having Cars and Person classes

Q1. Technical discussion on Machine Learning, Deep Learning Concepts and coding round.
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Q1. Technical discussion on Deep Learning and Computer Vision.
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Q1. Related to networking
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Q1. Related to switch router
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Q2. Communication skill test
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Q1. Communication skillsa
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Q1. Active Directory Configuration and it’s uses
Ans. 
Active Directory is a directory service used by Windows networks to store information about users, computers, and resources.
• Centralized management of network resources

• Authentication and authorization of users and computers

• Group policy management for security and configuration settings

• Single sign-on for users to access multiple resources

• Integration with other Microsoft services like Exchange Server and SharePoint
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Q2. What is domain controller
Ans. 
A domain controller is a server that manages network security, authentication, and access control for a domain.
• Manages user authentication and authorization within a domain

• Stores user account information and security policies

• Controls access to network resources

• Replicates data and changes to other domain controllers in the network

• Examples: Active Directory Domain Services (AD DS) in Windows Server
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Q3. User cases and how would you solve it
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Q1. General intro about profile
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Q1. Deep diving into experience
Ans. 
I have extensive experience in managing office operations and ensuring smooth workflow.
• Managed day-to-day administrative tasks such as scheduling appointments, coordinating meetings, and handling correspondence.

• Implemented efficient filing systems and document management processes to improve organization and accessibility.

• Developed and implemented office policies and procedures to enhance productivity and streamline op...read more
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Basic of react hooks, functional component,class component and indepth of javascript like polyfill of higher-order functions

React , design patterns , logical questions in js of clousers and currying, problem solving

Q1. The technical manager asked the questions on my previous projects and he shared his vision like he want to hire someone who will be a individual contributor and able to handel from product design to coding...read more
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Q2. - what do you know anything about AWS. - what is the microservices
Ans. 
AWS is a cloud computing platform that provides a wide range of services. Microservices are a software development approach where applications are built as a collection of small, independent services.
• AWS is a popular cloud computing platform that offers services such as computing, storage, and databases.

• AWS provides a range of tools and services for developers, including AWS Lambda, Amazon EC2, and Amazon S3.

• Microservi...read more
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Q1. I the first round HR will ask you to tell about yourself. My Introduction format was as follows- 1.Good Morning/Afternoon/Evening 2.Thankyou For the opportunity greeting 3.Name and home town 4.Pursuing co...read more
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Q1. Where you belong from ? Tell me about schooling ? what are your carrier Goals ? Are you comfortable with night shift ?
Ans. 
I am from XYZ city and completed my schooling from ABC school. My career goal is to become a successful Technical Analyst. Yes, I am comfortable with night shifts.
• I belong to XYZ city.

• I completed my schooling from ABC school.

• My career goal is to become a successful Technical Analyst.

• I am comfortable with night shifts.
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