Billennium Senior Java Developer Interview Questions and Answers

Q1. Spring boot migration
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Q1. Will you be flexible?
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Logical reasoning and Aptitude

Functions with Pointers and strings concepts

Q1. Mainly on Pointers and Dynamic Memory Allocation of 2-D Array
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Q2. Structure Padding and Packing
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60mintues DSA level coding exam

Q1. Strecture of sql statement
Ans. 
SQL statements are used to interact with databases by performing operations like querying, updating, and deleting data.
• SQL statements are made up of keywords like SELECT, INSERT, UPDATE, DELETE, etc.

• They are structured in a specific order, with clauses like WHERE, ORDER BY, GROUP BY, etc.

• Tables are referenced using their names, and conditions are specified to filter data.

• Joins can be used to combine data from multiple
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Had a DSA question based on maps, CSS related MCQ and prototype related MCQ

Q1. Solved basic DSA question hashmap
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Q1. What are oops concepts in java, explain real time scenario
Ans. 
OOPs concepts in Java include inheritance, polymorphism, encapsulation, and abstraction.
• Inheritance allows a subclass to inherit properties and methods from a superclass.

• Polymorphism allows objects to take on multiple forms and behave differently based on their context.

• Encapsulation hides the implementation details of an object and only exposes necessary information.

• Abstraction allows for the creation of abstract class...read more
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Q2. Uses of interface, inheritance
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Interfaces define contracts for behavior, while inheritance allows for code reuse and polymorphism.
• Interfaces allow for loose coupling and abstraction, enabling multiple implementations of the same behavior.

• Inheritance allows for code reuse and extension of existing classes, reducing code duplication.

• Polymorphism allows objects of different classes to be treated as if they were of the same class, simplifying code and i
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Q3. SQL query for join of tables
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SQL query for joining tables
• Use JOIN keyword to combine two or more tables based on a related column

• Specify the columns to be selected using SELECT keyword

• Use ON keyword to specify the condition for joining the tables

• Different types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL OUTER JOIN
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Q4. Java concepts used in your project
Ans. 
Used Java concepts such as inheritance, polymorphism, and exception handling in my project.
• Implemented inheritance to create a base class and derived classes with specific functionalities.

• Utilized polymorphism to allow objects of different classes to be treated as if they were of the same class.

• Implemented exception handling to handle errors and prevent program crashes.

• Used interfaces to define a set of methods that a ...read more
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Q5. Overloading vs overriding, practical uses
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Overloading is having multiple methods with the same name but different parameters. Overriding is having a method in a subclass with the same name and parameters as a method in the superclass.
• Overloading is used to provide different ways to call a method with different parameters

• Overriding is used to provide a specific implementation of a method in a subclass

• Overloading is resolved at compile-time while overriding is r...read more
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Q1. Lookup vs graphlookup in mongodb
Ans. 
Lookup is used to perform a left outer join in MongoDB, while graphlookup is used to perform recursive graph traversal.
• Lookup is used to perform a left outer join between two collections in MongoDB.

• Graphlookup is used to perform recursive graph traversal in a collection that contains graph data.

• Lookup can only perform a single level join, while graphlookup can perform multiple levels of traversal.

• Lookup is faster than
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Q2. Count frequency of each character in string
Ans. 
Use a hashmap to count the frequency of each character in a string.
• Create a hashmap to store characters as keys and their frequencies as values.

• Iterate through the string and update the hashmap accordingly.

• Return the hashmap with character frequencies.
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Q1. Create a rest api all the way from controller to repository using NOTEPAD
Ans. 
Creating a REST API from controller to repository using NOTEPAD
• Create a controller class with mapping annotations for REST endpoints

• Implement service layer to handle business logic and interact with repository

• Define repository interface with methods for data access operations

• Use Spring Boot for easy setup and configuration

• Test API endpoints using tools like Postman
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Q2. Couldnt write custom mongodb query at repository layer in notepad which rejected my candidature.
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Q1. SDLC process and how it is implemented in project
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Q2. About projects, it's Objective, the role I have worked, output
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Q3. Data structure, DBMS concepts
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