NJ Technologies Java Full Stack Developer Interview Questions and Answers

Code was of leetcode medium level.

Q1. Easy level DS code
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Q2. Question related to database
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Q1. Questions related to SQL
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Q2. Inner join of three tables
Ans. 
Inner join of three tables in SQL
• Use the JOIN keyword to combine three tables based on a common column

• Specify the columns to select from each table

• Use the ON keyword to specify the join condition
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Q3. What is cross join
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Cross join is a type of join operation in SQL that returns the Cartesian product of two tables.
• Cross join does not require any matching condition between the tables.

• It combines each row from the first table with every row from the second table.

• Cross join can result in a large number of rows if the tables are big.

• Example: SELECT * FROM table1 CROSS JOIN table2;
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Q1. Oops? .net core features
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Round duration - 180 minutes
Round difficulty - Hard

The test link had 3 days expiry so I could attempt test anytime. It was conducted on doselect.com

Q1. 
Equilibrium Indices in a Sequence
You are given an array/list named 'SEQUENCE', which consists of 'N' integers. The task is to identify all equilibrium indices in this sequence.
Explanation:
An equilibr...read more
Ans. 
The task is to find the equilibrium indices of a given sequence, where the sum of elements at lower indices is equal to the sum of elements at higher indices.
• Iterate through the sequence and calculate the total sum of all elements

• Initialize a left sum and right sum as 0

• For each index, update the left sum and right sum and check if they are equal

• If they are equal, add the index to the equilibrium indices

• Return the equil
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Round duration - 60 minutes
Round difficulty - Medium

Video interview round wherein I was asked to wrote code for the problem statements given by the interviewer. The problems were mainly focused on advanced JS concepts like asynchonous progamming, timers, closures, and data structure problems around arrays, sets, linked list etc.

Q1. 
Rearrange Linked List Problem Statement
Given a singly linked list in the form 'L1' -> 'L2' -> 'L3' -> ... 'Ln', your task is to rearrange the nodes to the form 'L1' -> 'Ln' -> 'L2' -> '...read more
Ans. 
The task is to rearrange the nodes of a singly linked list in a specific order without altering the data of the nodes.
• Iterate through the linked list to find the middle node using the slow and fast pointer technique.

• Reverse the second half of the linked list.

• Merge the first and reversed second half of the linked list alternatively to get the desired order.
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Round duration - 30 minutes
Round difficulty - Easy

This was the last round with HR wherein they judged cultural fit and there was discussion on things like my expectations v/s their expectations etc.

Round duration - 30 minutes
Round difficulty - Easy

This round mainly consisted of some questions on advanced JS topics like Execution Context, Callback queue, Micro task queue, Promises, etc.

Round duration - 60 minutes
Round difficulty - Medium

This round was more technical compared to the previous one. The interviewer was a senior developer. If questions were not answered, answers would be given/explained.

Q1. What are some aggregate operators in MongoDB?
Ans. 
Aggregate operators in MongoDB are used for data aggregation and manipulation.
• Some aggregate operators in MongoDB include $sum, $avg, $min, $max, $push, $addToSet, $first, $last, $project, $match, $group, $sort, $limit, $skip.

• Example: db.collection.aggregate([{$group: {_id: '$field', total: {$sum: '$value'}}}])
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Round duration - 30 minutes
Round difficulty - Easy

This round was mainly to assess my experience level, roles, and responsibilities from my previous company. Salary negotiations also happened here.

Aptitude test was of 1 hr

It was about 1 hr duration

Q1. What do you know about oops
Ans. 
Object-oriented programming paradigm focusing on objects and classes
• Encapsulation: Bundling data and methods that operate on the data into a single unit (object)

• Inheritance: Ability of a class to inherit properties and behavior from another class

• Polymorphism: Ability to present the same interface for different data types

• Abstraction: Hiding the complex implementation details and showing only the necessary features
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Q2. Tell me about encapsulation
Ans. 
Encapsulation is the concept of bundling data and methods that operate on the data into a single unit.
• Encapsulation helps in hiding the internal state of an object and restricting access to it.

• It allows for better control over the data by preventing outside interference.

• Encapsulation also promotes code reusability and modularity.

• Example: In object-oriented programming, classes encapsulate data fields and methods to ope
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Q1. How do you manage your team
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Q2. Why should I hire you
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2 Query question and 3 coding questions

Q1. Basic oops , Java script and Networking questions.
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Q2. What is object orienteered programming.
Ans. 
Object oriented programming is a programming paradigm based on the concept of objects, which can contain data and code.
• Objects are instances of classes, which define the structure and behavior of the objects.

• Encapsulation, inheritance, and polymorphism are key principles of object oriented programming.

• Example: Java, C++, Python are popular languages that support object oriented programming.
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Q3. Different Events in java script
Ans. 
Events in JavaScript are actions or occurrences that happen in the browser that the code can respond to.
• Events can be triggered by user actions (like clicking a button), browser actions (like page load), or system events (like a timer expiring)

• Event listeners are used to listen for and respond to events

• Common events include click, mouseover, keydown, submit, etc.
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Q4. Event listeners
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Project , coding question, DBMS

Q1. Basic personal details
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2 DSA questions Both are from DP

Q1. 2 Questions , 1 is DSA
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Q2. Second question is Puzzle
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Q1. Explain basics of c#
Ans. 
C# is a programming language developed by Microsoft for building a wide range of applications on the .NET framework.
• C# is an object-oriented language with features like classes, inheritance, and polymorphism.

• It is strongly typed, meaning variables must be declared with a specific data type.

• C# supports modern programming concepts like async/await for asynchronous programming.

• It is commonly used for developing desktop, w...read more
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Q2. C# basics oops sql server
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