Cognizant Senior Java Developer Interview Questions, Process, and Tips

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
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Q1. Difference between HashMap and TreeMap? Internal working of HashMap?
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Q2. Functional Interface?
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Q3. Singleton Class?
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Q4. What is Eureka Server?
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Q5. How to handle Exception in SpringBoot?
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Q6. Find the average sal of employee in each department using java 8 Stream?
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Q7. What is circuit Breaker?
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Q8. What is docker and kubernates?
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Q1. Project related questions, architecture, exception handling, Kafka use case.
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Q2. Oops question functional interface, marker interface.
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Q3. Memory leaks and how to avoid the same.
Ans. 
Memory leaks occur when a program allocates memory but does not release it, leading to inefficient memory usage.
• Use tools like profilers to identify memory leaks in Java applications.

• Avoid creating unnecessary objects and ensure proper garbage collection.

• Avoid static references to objects that can prevent them from being garbage collected.

• Close resources like files, database connections, and streams after use to preven
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Q4. Multi threading question
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Q1. Pom related questions how many scope available.
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Q2. Agile related questions
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Q3. Comparable vs comparator
Ans. 
Comparable is an interface used for natural ordering, while Comparator is an interface used for custom ordering.
• Comparable is implemented by the class itself to define the natural ordering of objects.

• Comparator is implemented by a separate class to define custom ordering of objects.

• Example: String class implements Comparable interface for natural ordering, while Collections class uses Comparator for custom sorting.
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The first round was an interview conducted with a GENAI virtual bot.

Q1. Internal architecture of Spring boot, how enable autoconfiguration works
Ans. 
Spring Boot uses autoconfiguration to automatically configure the Spring application based on dependencies and properties.
• Spring Boot autoconfiguration is achieved through @EnableAutoConfiguration annotation

• Autoconfiguration classes are located in the org.springframework.boot.autoconfigure package

• Autoconfiguration classes are conditionally applied based on the presence of specific classes or properties
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Q2. Questions mostly on microservices and coding question on restTemplate
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