HCLTech Senior Java Developer Interview Questions and Answers

A sequence was provided: 4181, 2684, 1597, 987, 610.
first 2 are given and write code for other value calculation using java 8

The second question required writing a reverse of a palindrome using both Java 8 streams. I was able to successfully write both and clear the first round.

Q1. Interviewer was himself not knowing anything as it was walkin drive he was sitting infront of me and checking questions on phone Introduction that he inturrepted in between when I was introducing myself
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Q2. What are the features of Java 17, specifically related to sealed classes, including their syntax and necessity, along with the potential errors encountered when invoking a sealed class?
Ans. 
Java 17 introduces sealed classes to restrict inheritance and improve code maintainability.
• Sealed classes are declared using the 'sealed' keyword followed by the permitted subclasses.

• Subclasses of a sealed class must be either final or sealed themselves.

• Errors may occur when trying to extend a sealed class with a non-permitted subclass.
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Q3. Java 8 feathers stream api, functional interface, Intermittent operator ,Ternary operator, Prediction,Bi predicate. Answered all successfully
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Q4. Draw low level design of implementation of notify me if item is back in stock in a ecommerce application
Ans. 
Implementation of 'notify me if item is back in stock' feature in an ecommerce application
• Create a database table to store user notifications for out-of-stock items

• Implement a service to check item availability and send notifications to subscribed users

• Provide a user interface for users to subscribe to notifications for specific items
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Q5. All design patterns which I know. Asked me to implement adapter pattern on paper
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Q6. Then given a problem that concurrent way perform operation on excell to decrease the response time
Ans. 
Utilize Java concurrency features to optimize Excel operations for faster response times.
• Use Java's ExecutorService to manage a pool of threads for concurrent processing.

• Implement parallel streams to process large datasets in Excel efficiently.

• Utilize Apache POI for reading/writing Excel files in a multi-threaded manner.

• Consider using CompletableFuture for asynchronous operations on Excel data.

• Batch operations to minim...read more
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Q1. Flow of micro services, annotations of boot
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Q2. Sorting program
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Q1. Project flow,team management
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Q2. Collection questions
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Q1. Normal hr questions,about changing jobs and etc.
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Q2. Salary negotiation
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Q1. @restcontroller
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Q2. Controller and responsebody
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Q1. Abstract class vs interface
Ans. 
Abstract class is a class that can have abstract methods and concrete methods, while interface is a contract that defines methods that a class must implement.
• Abstract class can have constructors, member variables, and non-abstract methods.

• Interface can only have abstract methods and constants.

• A class can implement multiple interfaces but can only extend one abstract class.

• Example: Abstract class - Animal with abstract ...read more
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Q2. Spring vs spring boot framework
Ans. 
Spring is a framework that provides comprehensive infrastructure support, while Spring Boot is a tool that simplifies Spring application development.
• Spring is a comprehensive framework that provides various modules for different functionalities like Spring MVC, Spring Security, Spring Data, etc.

• Spring Boot is a tool that simplifies the setup and configuration of Spring applications by providing defaults and auto-config...read more
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