Cognizant Java Technical Lead Interview Questions, Process, and Tips

Q1. Spring Boot, Microservice Basic
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Q1. RestAPI implementation
Ans. 
RestAPI implementation involves creating web services using HTTP methods to interact with data.
• Use HTTP methods like GET, POST, PUT, DELETE to perform CRUD operations on resources

• Implement endpoints with appropriate request and response formats (JSON, XML)

• Secure API with authentication and authorization mechanisms like OAuth

• Document API using tools like Swagger for easy consumption by clients
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Q1. Use of static in main function
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Using static in main function allows it to be called without creating an instance of the class.
• Static in main function allows it to be called directly without creating an object of the class.

• Static methods can be called using the class name itself, without creating an object.

• Example: public static void main(String[] args) { }
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Data Structures, logical questions

Q1. Springboot, microservices, Data sources,architecture design
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Q1. General HR disccussion
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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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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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Q1. Difference between hashmap and hash table
Ans. 
HashMap is non-synchronized and allows null values, while HashTable is synchronized and does not allow null values.
• HashMap is non-synchronized, meaning it is not thread-safe, while HashTable is synchronized and thread-safe.

• HashMap allows null values for both keys and values, while HashTable does not allow null keys or values.

• HashMap is generally preferred for non-thread-safe applications, while HashTable is used in mul
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Q2. Static block related questions
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Q3. Arraylist and linkedlist question
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Q1. Transactions in springboot
Ans. 
Transactions in Spring Boot manage database operations as a single unit of work to ensure data integrity.
• Spring Boot provides support for declarative transaction management using @Transactional annotation.

• Transactions can be configured at class or method level.

• Transactions can be rolled back in case of exceptions to maintain data consistency.

• Example: @Transactional annotation on a service method ensures that all databa...read more
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Q2. Difference between arraylist and linked list

Ans. 

ArrayList is resizable array implementation, LinkedList is doubly linked list implementation.

• ArrayList uses dynamic array to store elements, LinkedList uses doubly linked list.

• ArrayList is faster for accessing elements by index, LinkedList is faster for adding/removing elements.

• Example: ArrayList arrList = new ArrayList<>(); LinkedList linkedList = new LinkedList<>();

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