CitiusTech Mern Full Stack Developer Interview Questions and Answers

Q1. Dependency injection
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Q2. Check all oop questions
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Q3. Array related dsa
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Q1. Java vs Javascript , Meaning of Synchronization in Java , Multihreading in Js
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Java is a backend language, Javascript is a frontend language. Synchronization in Java ensures only one thread can access a resource at a time. JavaScript is single-threaded but can handle asynchronous operations using callbacks, promises, and async/await.
• Java is a backend language used for server-side development, while JavaScript is a frontend language used for client-side scripting.

• Synchronization in Java is a techn...read more
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Q2. Write a pojo class to display the Employee Details,Pojo vs Bean
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A Pojo class is a simple Java class that contains only private fields, public getters and setters, and no-arg constructor.
• Create private fields for employee details like name, id, salary, etc.

• Generate public getters and setters for each field.

• Include a no-arg constructor in the class.

• Example: public class Employee { private String name; private int id; public String getName() { return name; } public void setName(String...read more
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Q3. How to to compare two objects with same class (equals & Hashcode methods)
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To compare two objects with the same class, override the equals and hashCode methods in the class.
• Override the equals method to compare the fields of the objects for equality.

• Override the hashCode method to generate a unique hash code based on the object's fields.

• Ensure that the equals and hashCode methods are consistent with each other.

• Example: public class Person { private String name; private int age; }
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Q4. Springboot questions basics like How to connect to 2 databases at a time How to change the table name in entity class(@Table)
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Q5. JPA Repository inbuilt methods
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JPA Repository provides inbuilt methods for common database operations in Spring applications.
• JPA Repository provides methods like save(), findById(), findAll(), deleteById(), etc.

• These methods help in performing CRUD operations on entities without writing custom queries.

• For example, userRepository.save(user) saves a user entity to the database.
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Q1. Java Related Questions
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Q1. Angular Question In Deep
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Q1. Javascript Question Advance
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Project Architecture, Cloud Items, Load balancing etc.

Q1. Tell me about your self
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Q2. About technical questions
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Q3. About current project
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Q1. Why do you want to leave your current workplace?
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Q1. Based on your tech skills mentioned in your resume
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Q1. About the company and compensation
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Q1. Explain MVC Lifecycle.
Ans. 
MVC Lifecycle is the sequence of events that occur in the Model-View-Controller architectural pattern.
• MVC stands for Model-View-Controller.

• The lifecycle starts with a user request.

• The controller receives the request and processes it.

• The controller updates the model with the necessary data.

• The view is then updated with the updated model data.

• The updated view is sent back to the user as a response.
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Q2. Create a new Thread and explain the ways to create Threads in Java
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Creating Threads in Java
• Extending the Thread class and overriding the run() method

• Implementing the Runnable interface and passing it to a Thread constructor

• Using Executor framework to create and manage threads

• Using Callable and Future interfaces to create threads that return values
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Q3. What is HashMap? Difference between List and HashMap?
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HashMap is a data structure that stores key-value pairs. List is a collection of ordered elements.
• HashMap allows fast retrieval of values based on keys.

• List maintains the order of elements and allows duplicates.

• HashMap uses hashing to store and retrieve elements.

• List uses indexing to access elements.

• HashMap is not thread-safe while List is thread-safe.

• Example: HashMap map = new HashMap<>(); map.put("ap...read more
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Q4. Difference between HashMap and HashTree
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HashMap is a non-synchronized implementation of Map interface while HashTree is a synchronized implementation of Map interface.
• HashMap is faster than HashTree as it is non-synchronized.

• HashTree is thread-safe while HashMap is not.

• HashMap allows one null key and multiple null values while HashTree does not allow null keys or values.

• HashTree maintains the order of elements while HashMap does not.

• HashMap is generally used...read more
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Q5. What class is used to connect with the Database?
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The class used to connect with the Database depends on the programming language and framework being used.
• In Java, the class used is usually DriverManager or DataSource.

• In Python, the class used is usually psycopg2 or mysql-connector.

• In PHP, the class used is usually PDO or mysqli.

• The specific class used may also depend on the type of database being used, such as MySQL, PostgreSQL, or MongoDB.
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Q6. What are the classes needed to create a GET REST API?
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Classes needed to create a GET REST API
• Controller class to handle the request

• Service class to perform business logic

• Repository class to interact with database

• Model class to define data structure

• RequestMapping annotation to map the URL
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Q7. What is an Interface? What is default method in Interface?
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An interface is a blueprint of a class. Default method is a method in an interface with a default implementation.
• An interface defines a set of methods that a class must implement

• Default method provides a default implementation for a method in an interface

• Default methods were introduced in Java 8

• Default methods can be overridden by implementing classes
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Q8. How is an interface used?
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An interface is used to define a contract between two components in a system.
• An interface defines a set of methods that a class must implement.

• Interfaces are used to achieve abstraction and loose coupling.

• Interfaces are used to create reusable code.

• Interfaces are used to enable polymorphism.

• Interfaces are used in many programming languages, including Java, C#, and TypeScript.
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Q9. Explain polymorphism in Java
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Polymorphism is the ability of an object to take on many forms.
• Polymorphism allows objects of different classes to be treated as if they are objects of the same class.

• It can be achieved through method overloading and method overriding.

• Example: A parent class Animal can have multiple child classes like Dog, Cat, and Cow. All these child classes can have their own implementation of the method 'makeSound', which can be ca...read more
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