40+ DMart Interview Questions and Answers

Pessimistic locking is when a resource is locked for a long time, while optimistic locking is when a resource is locked only when it is being modified.

• Pessimistic locking involves locking a resource for a long time to prevent other users from accessing it.

• Optimistic locking involves locking a resource only when it is being modified, allowing other users to access it in the meantime.

• Pessimistic locking is useful when conflicts are likely to occur, while optimistic locking is u...read more

Absolute Xpath is the complete path from the root element to the desired element, while Relative Xpath is the path based on the current element.

• Absolute Xpath starts with a single slash (/) and is more specific but less flexible.

• Relative Xpath starts with a double slash (//) and is more flexible but less specific.

• Absolute Xpath is more prone to breaking if the structure of the page changes.

• Relative Xpath is easier to maintain and update as it is based on the element's positio...read more

LinkedList is preferred for constant modification due to faster insertion and deletion times.

• LinkedList is preferred for constant modification because it has faster insertion and deletion times compared to ArrayList.

• LinkedList allows for easy insertion and deletion of elements without the need to shift other elements, making it more efficient for constant modifications.

• ArrayList is better for random access and iterating through elements, while LinkedList is better for frequen...read more

Check if two strings are anagrams of each other

• Create a character count array for both strings

• Compare the character count arrays

• If they are equal, the strings are anagrams

High severity and low priority: spelling mistake in a non-critical feature. High priority and low severity: UI color change request.

• High severity and low priority: spelling mistake in a non-critical feature

• High priority and low severity: UI color change request

REST endpoints for a ticket booking system

• GET /events - get list of available events

• GET /events/{id} - get details of a specific event

• POST /events/{id}/tickets - book tickets for an event

• GET /bookings - get list of all bookings

• GET /bookings/{id} - get details of a specific booking

• PUT /bookings/{id} - update a booking

• DELETE /bookings/{id} - cancel a booking

HashMap is a data structure that stores key-value pairs using hashing. An abstract class is a class that cannot be instantiated.

• HashMap uses hashing to store key-value pairs for efficient retrieval.

• Abstract classes cannot be instantiated and can have abstract methods that must be implemented by subclasses.

• Example: HashMap map = new HashMap<>();

POM stands for Page Object Model. It is a design pattern used in automation testing to create a structured and maintainable framework.

• POM separates the test scripts from the web elements, making the code more readable and reusable.

• Each web page is represented as a separate class, containing its own web elements and methods.

• POM improves test maintenance by reducing code duplication and enhancing code reusability.

• It enhances collaboration between developers and testers as they ...read more

Program to find the largest and smallest integer in a program

• Iterate through the array of integers to find the largest and smallest values

• Initialize variables to store the largest and smallest values, update them as needed

• Handle edge cases like empty array or array with only one element

• Return the largest and smallest values found

The UNIX command for copying a file is 'cp'.

• The 'cp' command is used to create a copy of a file or directory.

• The basic syntax of the 'cp' command is 'cp source_file destination_file'.

• If the destination file already exists, it will be overwritten unless the '-i' option is used.

• To copy a directory and its contents, the '-r' or '-R' option is used.

• Examples: 'cp file1.txt file2.txt' or 'cp -r directory1 directory2'

Java performance and query optimization in Oracle

• Use prepared statements to avoid SQL injection and improve performance

• Use indexes to speed up query execution

• Avoid using SELECT * and only select necessary columns

• Use connection pooling to reuse database connections

• Use caching to reduce database round trips

• Tune database parameters like buffer cache and shared pool size

• Use profiling tools to identify performance bottlenecks

Implement HashMap, find duplicate count, and find pairs with sum matching target in an optimized way.

• Implement HashMap using arrays and linked lists for collision resolution.

• Use a HashMap to store element counts and find duplicates efficiently.

• Use a two-pointer approach to find pairs with sum matching the target in O(n) time complexity.

Test attribute is used to define a test method, while TestCase attribute is used to define a test case class.

• Test attribute is used to mark a method as a test method in a test class.

• TestCase attribute is used to mark a class as a test case class containing multiple test methods.

• Test attribute is used in frameworks like NUnit, JUnit, etc.

• TestCase attribute is used in frameworks like NUnit, JUnit, etc.

Print duplicate values from a String using do-while loop

• Create a HashSet to store unique values

• Use a do-while loop to iterate through the String

• Check if the HashSet already contains the current character, if yes, print it as a duplicate

NoSQL databases are non-relational databases that do not require a fixed schema, while SQL databases are relational databases that use structured query language.

• NoSQL databases are schema-less, allowing for flexible data models.

• SQL databases use a fixed schema with tables and rows.

• NoSQL databases are horizontally scalable, making them suitable for big data applications.

• SQL databases are vertically scalable, meaning they can only handle increased load by increasing the power o...read more

To make a Java class immutable, use final keyword and initialize all fields in constructor.

• Use final keyword for class and all fields

• Initialize all fields in constructor

• Do not provide setter methods

• Make sure to return a new instance in any method that modifies the state

Create a class with other objects as immutable

• Use final keyword to make class immutable

• Make all fields private and final

• Do not provide setter methods, only getter methods

• If class contains mutable objects, make sure to return a copy of them in getter methods

Listen to their perspectives, encourage open communication, find common ground, and work towards a compromise.

• Encourage open communication to understand each employee's perspective

• Listen actively and show empathy towards their opinions

• Find common ground and areas of agreement to build upon

• Work towards a compromise that addresses the concerns of all parties involved

To find an element within a frame using Selenium, switch to the frame and then locate the element using appropriate locators.

• Use the 'switchTo().frame()' method to switch to the desired frame

• Locate the element within the frame using locators like ID, class name, XPath, etc.

• Perform actions on the element as required

Shorten URL design involves generating a unique short code for a long URL to save space and improve usability.

• Use a hashing algorithm to generate a unique short code for each URL

• Store the mapping between short code and long URL in a database

• Redirect users to the long URL when they access the short URL

• Consider adding expiration time for short URLs to prevent abuse

• Provide analytics to track usage of short URLs

Print duplicate values from a string as an array of strings

• Iterate through each character in the string

• Use a hashmap to store the frequency of each character

• Print characters with frequency greater than 1 as duplicates

Closures in JavaScript are functions that have access to their own scope, as well as the scope in which they were defined.

• Closures allow functions to access variables from an outer function even after the outer function has finished executing.

• They are created whenever a function is defined within another function.

• Closures are commonly used to create private variables and functions in JavaScript.

SQL query to find 2nd highest salary

• Use the ORDER BY clause to sort salaries in descending order

• Use the LIMIT clause to retrieve the second row

Layout optimisation in Xamarin forms involves improving performance and user experience by efficiently arranging UI elements.

• Use ListView instead of StackLayout for long lists to improve performance.

• Avoid nesting multiple layouts within each other to reduce complexity.

• Utilize Grid layout for more complex UI designs.

• Use RelativeLayout for positioning elements relative to each other.

• Implement caching mechanisms for frequently used data to reduce loading times.

Distributed system design involves breaking down a system into smaller components that communicate and coordinate with each other over a network.

• Decompose the system into smaller services that can run independently

• Use messaging protocols like MQTT or AMQP for communication

• Implement fault tolerance and scalability measures

• Consider data consistency and synchronization across nodes

• Examples: microservices architecture, Apache Kafka for message streaming

EPIC stories can be divided into three levels: Epics, Features, and User Stories.

• Epics are high-level stories that are too big to be completed in a single sprint.

• Features are smaller stories that are derived from Epics and can be completed in a single sprint.

• User Stories are the smallest stories that are derived from Features and can be completed in a single sprint.

• Each level of story is broken down into smaller, more manageable pieces.

• For example, an Epic might be 'Improve t...read more

Function to calculate factorial of a number

• Create a function that takes an integer as input

• Use a loop to multiply the number by all integers from 1 to the input number

• Return the final result

The Bull Whip Effect refers to the phenomenon of demand variability amplifying as it moves up the supply chain.

• It is a supply chain management concept.

• Demand fluctuations at the end of the supply chain are magnified as they move upstream.

• Causes include lack of communication, forecasting errors, and order batching.

• Results in inventory inefficiencies, excess costs, and poor customer service.

• Example: A retailer experiences small fluctuations in customer demand, but the manufactu...read more

Microservices architecture is an architectural style that structures an application as a collection of loosely coupled services.

• Each service is self-contained and can be developed, deployed, and scaled independently.

• Services communicate with each other over lightweight protocols like HTTP or messaging queues.

• Microservices allow for flexibility, scalability, and resilience in large and complex applications.

• Examples of companies using microservices architecture include Netflix,...read more

Print tables from 1 to 20 in one sequential order.

• Use a loop to iterate from 1 to 20

• Inside the loop, multiply the current number with each number from 1 to 10

• Print the result in a formatted table

I have 3 years of experience developing mobile apps for both iOS and Android platforms.

• Developed mobile apps using Swift for iOS and Java/Kotlin for Android

• Experience with mobile app design principles and user interface development

• Worked on integrating APIs and third-party libraries for enhanced functionality

To reverse a string 'Ecommerce', you can iterate through the characters in the string and build a new string in reverse order.

• Iterate through the characters of the string from end to start

• Append each character to a new string to build the reversed string

• Return the reversed string as the result

Managing stakeholder expectations, resource constraints, scope changes, and communication issues are common challenges in projects.

• Managing stakeholder expectations is crucial for project success

• Dealing with resource constraints can impact project timelines and quality

• Handling scope changes requires effective change management processes

• Communication issues can lead to misunderstandings and delays

Batch normalization is a technique used to improve the training of deep neural networks by normalizing the input of each layer.

• Batch normalization normalizes the input of each layer by adjusting and scaling the activations.

• It helps in reducing internal covariate shift, making training faster and more stable.

• Batch normalization is applied to mini-batches of data during training.

• Layer normalization is similar to batch normalization but normalizes the activations of each layer i...read more

Symmetry trees in Catboost are used to improve the model's performance by exploiting the symmetry of categorical features.

• Symmetry trees are a type of decision tree used in Catboost to handle categorical features.

• They exploit the symmetry of categorical features to improve the model's performance.

• Symmetry trees help in reducing overfitting and improving generalization.

• They are particularly useful when dealing with high-cardinality categorical features.

• An example of a symmetry...read more

To reverse a string, iterate through the characters and swap the first and last characters until reaching the middle.

• Create a character array from the input string

• Use two pointers, one starting from the beginning and one from the end, and swap the characters at those positions

• Continue swapping until the pointers meet in the middle

Microservices architecture is an architectural style that structures an application as a collection of loosely coupled services.

• Each service is self-contained and can be developed, deployed, and scaled independently.

• Services communicate with each other over lightweight protocols like HTTP or messaging queues.

• Microservices allow for better scalability, flexibility, and resilience compared to monolithic architectures.

• Examples of companies using microservices architecture includ...read more

Joins in SQL are used to combine rows from two or more tables based on a related column between them.

• Joins are used to retrieve data from multiple tables based on a related column

• Types of joins include INNER JOIN, LEFT JOIN, RIGHT JOIN, and FULL JOIN

• Example: SELECT * FROM table1 INNER JOIN table2 ON table1.column = table2.column

Handle difficult customers by listening, empathizing, setting boundaries, and finding solutions.

• Listen actively to understand their concerns

• Empathize with their emotions and frustrations

• Set clear boundaries for acceptable behavior

• Find mutually beneficial solutions to resolve the issue

A For loop is used to iterate over a collection of items and perform a set of actions for each item.

• Initialize a counter variable before the loop

• Set the condition for the loop to continue based on the counter variable and the length of the array

• Increment the counter variable after each iteration

• Access each element in the array using the counter variable