50+ Java R & D Interview Questions and Answers

Rearrange array in consecutive pair multiplication in descending order.

• Create a new array to store the multiplied values

• Use a loop to iterate through the original array and multiply consecutive pairs

• Write a compare function to sort the new array in descending order

Answers to common technical questions in a software engineering interview

• A transaction in DBMS is a sequence of operations that must be treated as a single unit of work. ACID properties ensure reliability and consistency of transactions.

• A thread is a lightweight process that shares memory and resources with other threads in the same process. A process is a separate instance of a program.

• Common Linux commands include ls, cd, mkdir, rm, and grep.

• sudo is used to run commands wit...read more

Design algorithm and database for seat booking system of BookMyShow and handle failed payments.

• Create a database with tables for movies, theaters, seats, bookings, and payments

• Use a locking mechanism to prevent double booking of seats

• If payment fails, release the locked seats and notify the user

• Write a query to get the timestamp in SQL: SELECT CURRENT_TIMESTAMP;

Introduce new API version without breaking the previous one.

• Use versioning in the API endpoint URL

• Provide documentation for both versions

• Gradually phase out the old version

• Use backward-compatible changes

• Test thoroughly before releasing the new version

A program to perform basic arithmetic operations on fractional numbers and simplify the result.

• Create a Fraction class with numerator and denominator attributes

• Implement methods for addition, subtraction, multiplication, and division

• Use the Euclidean algorithm to simplify the result

• Handle edge cases such as dividing by zero or negative denominators

Print a pyramid pattern of numbers in O(n) time.

• Use nested loops to print the pattern.

• The outer loop will iterate from 1 to n.

• The inner loop will iterate from 1 to the current value of the outer loop.

• Print the inner loop variable and a space after each iteration.

• Print a new line after the inner loop completes.

Data structures and algorithms can be used to optimize server performance and improve scalability.

• Implement efficient data structures for storing and accessing data on the server

• Use algorithms to optimize server processes and reduce response times

• Implement caching algorithms to improve performance and reduce server load

• Use data structures to manage server resources and prioritize tasks

• Implement load balancing algorithms to distribute traffic evenly across multiple servers

Program to evaluate algebraic expression with given values

• Use a stack to keep track of operators and operands

• Iterate through the expression and push operands onto the stack

• When an operator is encountered, pop the top two operands and perform the operation

• Push the result back onto the stack

• Repeat until the entire expression has been evaluated

Program to find elements present in one array but not in other array

• Iterate through each element in the first array and check if it exists in the second array

• If not found, add it to a new array of unique elements

• Repeat the process for the second array to find elements unique to it

Tech stack selection depends on project requirements, team expertise, scalability, and budget.

• Analyze project requirements and choose a stack that fits best

• Consider team expertise and choose a stack that team is comfortable with

• Evaluate scalability requirements and choose a stack that can handle future growth

• Consider budget constraints and choose a stack that is cost-effective

• Research and compare different stacks to make an informed decision

NodeJS is fast, scalable and has a large community support.

• NodeJS is built on Chrome's V8 JavaScript engine which makes it fast and efficient.

• It is event-driven and non-blocking which makes it scalable for handling large amounts of data.

• NodeJS has a large community support with a vast number of libraries and modules available.

• It is also cross-platform compatible and can be used for both server-side and client-side development.

• Examples of popular NodeJS projects include Netfli...read more

stoi() function converts a string to an integer.

• stoi() is a C++ function that takes a string as input and returns an integer.

• It is used to convert a string of digits into an integer.

• It can also handle negative numbers and ignore leading whitespace.

• Example: int num = stoi("123"); // num is now 123

Find minimum number of coins for a given value using backtracking and dynamic programming.

• Backtracking involves exploring all possible solutions and choosing the best one.

• Dynamic programming involves breaking down the problem into smaller subproblems and solving them.

• For backtracking, we can start with the largest coin and keep subtracting it until we reach the target value.

• For dynamic programming, we can create a table to store the minimum number of coins needed for each val...read more

Program to find the largest palindromic substring in input string.

• Iterate through each character in the input string and check for palindromic substrings.

• Keep track of the largest palindromic substring found so far.

• Use dynamic programming or expand around center approach for efficient solution.

• Example: Input string 'babad', largest palindromic substring is 'bab' or 'aba'.

Program to find all triplets with a given sum in an array.

• Use three nested loops to iterate through all possible combinations of triplets.

• Check if the sum of the current triplet is equal to the given sum.

• Store the triplets that satisfy the condition in a list and return the list.

Program to evaluate a mathematical expression using stack

• Use a stack to store operands and operators

• Iterate through the expression and push operands onto the stack

• When an operator is encountered, pop operands from the stack, perform the operation, and push the result back onto the stack

• Continue until the entire expression is evaluated

• The final result will be the top element of the stack

Program to detect repeated word sequences

• Read input text and split into words

• Create a dictionary to store word sequences and their frequency

• Iterate through the words and check for repeated sequences

• Output the repeated sequences and their frequency

Code for finding the longest common substring in an array of strings.

• Iterate through the first string and check for all possible substrings

• Check if the substring is present in all other strings

• Keep track of the longest common substring found so far

• Return the longest common substring

SEO standards include optimizing website content, using relevant keywords, and building quality backlinks.

• Optimize website content with relevant keywords and meta tags

• Ensure website is mobile-friendly and has fast loading speed

• Build quality backlinks from reputable sources

• Use descriptive and unique page titles and URLs

• Regularly update website content and add new pages

• Avoid duplicate content and keyword stuffing

• Utilize social media to promote website and increase visibility

Arrow functions are shorter syntax for writing function expressions.

• Arrow functions do not have their own 'this' keyword.

• They cannot be used as constructors.

• They cannot be used as methods in objects.

• They have implicit return statements.

• They have a more concise syntax than normal functions.

Web server handles HTTP requests and responses, while application server executes application logic.

• Web server serves static content like HTML, CSS, JS files

• Application server executes dynamic code like Java, Python, Ruby

• Web server communicates with client, application server communicates with database

• Examples of web servers: Apache, Nginx, IIS

• Examples of application servers: Tomcat, JBoss, WebSphere

Higher-order components are functions that take a component and return a new component with additional functionality.

• Higher-order components (HOCs) are a pattern in React for reusing component logic.

• They are functions that take a component and return a new component with additional functionality.

• HOCs can be used for adding props, state, or lifecycle methods to a component.

• Examples of HOCs include connect() from React Redux and withRouter() from React Router.

The pillars of OOPS are Abstraction, Encapsulation, Inheritance, and Polymorphism.

• Abstraction: Hiding implementation details and showing only necessary information.

• Encapsulation: Binding data and functions together and restricting access to them.

• Inheritance: Creating new classes from existing ones, inheriting properties and methods.

• Polymorphism: Ability of objects to take on multiple forms and behave differently based on context.

The question asks to arrange a string based on the frequency of the characters.

• Create a dictionary to store the frequency of each character in the string.

• Sort the dictionary based on the frequency of characters in descending order.

• Create a new string by concatenating the characters in the sorted dictionary.

A system for managing college fests

• Create a website for event registration and ticketing

• Develop a mobile app for real-time updates and notifications

• Implement a database to store event details and participant information

• Integrate payment gateway for online transactions

• Include features for event scheduling, venue management, and volunteer coordination

Code to rearrange an array in maximum-minimum form.

• Sort the array in descending order.

• Create a new array and alternate between adding the maximum and minimum values from the sorted array.

• Return the new array.

• Time complexity: O(nlogn)

• Space complexity: O(n)

Find sum of k smallest numbers in a BST.

• Traverse the BST in-order and add the k smallest numbers to a sum variable.

• Use a priority queue to keep track of the k smallest numbers.

• If k is greater than the number of nodes in the BST, return the sum of all nodes.

• If k is 0, return 0.

Search an element in a rotated sorted array.

• Find the pivot point where the array is rotated

• Determine which half of the array the target element is in

• Perform binary search on that half of the array

• Handle edge cases such as duplicates and empty arrays

Code splitting is a technique to split code into smaller chunks to improve performance.

• Code is divided into smaller chunks that can be loaded on demand

• Reduces initial load time and improves performance

• Used in modern web development frameworks like React, Angular, and Vue

• Example: splitting a large JavaScript file into smaller modules

Code for time stamp in C

• Use the time.h header file

• Call the time() function to get the current time in seconds

• Convert the time to a string using strftime() function

• Use the format string to specify the desired format of the time stamp

Addition of 2 numbers represented by Linked List

• Traverse both linked lists simultaneously and add the corresponding nodes

• If the sum is greater than 9, carry over the 1 to the next node

• If one linked list is shorter than the other, pad it with 0's

• Return the sum as a new linked list

Tree shaking is a process of eliminating unused code in React applications.

• It is a part of the build process that removes dead code from the final bundle.

• It helps in reducing the size of the bundle and improving the performance of the application.

• It works by analyzing the code and identifying the parts that are not used.

• It is achieved through tools like webpack and babel.

• Example: If a component is not used in the application, tree shaking will remove it from the final bundle.

To cope with stress, it is important to practice self-care, seek support from others, and engage in stress-relieving activities.

• Practice self-care by getting enough sleep, eating well, and exercising regularly.

• Seek support from friends, family, or a therapist to talk about your feelings and get advice.

• Engage in stress-relieving activities such as meditation, yoga, or hobbies you enjoy.

• Set boundaries and prioritize tasks to avoid feeling overwhelmed.

• Take breaks and practice re...read more

NoSQL databases are non-relational and flexible, while SQL databases are relational and structured.

• NoSQL databases are better suited for handling unstructured data

• SQL databases are better suited for handling structured data

• NoSQL databases are horizontally scalable

• SQL databases are vertically scalable

• Examples of NoSQL databases include MongoDB and Cassandra

• Examples of SQL databases include MySQL and PostgreSQL

Reverses a linked list in groups of k

• Break the linked list into groups of k nodes

• Reverse each group individually

• Connect the reversed groups back together

Reverse a linked list

• Iteratively swap the next and previous pointers of each node

• Use three pointers to keep track of the current, previous, and next nodes

• Update the head pointer to the last node after reversing

Topological sort is a linear ordering of vertices in a directed acyclic graph.

• Topological sort is used to find a linear ordering of vertices in a directed acyclic graph.

• It is commonly implemented using depth-first search (DFS) algorithm.

• The algorithm starts by visiting a vertex and then recursively visits all its adjacent vertices before adding it to the result list.

• Topological sort is not possible if the graph has cycles.

Topic description

• Pointer 1

• Pointer 2

• Pointer 3

Topological sorting is a linear ordering of vertices in a directed acyclic graph where for every directed edge uv, vertex u comes before v.

• Topological sorting is used in scheduling tasks, such as in project management or task scheduling algorithms.

• It can be implemented using depth-first search (DFS) algorithm.

• Kahn's algorithm is another popular method for topological sorting.

• Example: Given a graph with vertices A, B, C and directed edges A->B, A->C, B->C, the topological sort...read more