BT Group Senior Java Developer Interview Questions and Answers

Q1. Sql related ques mege into, rank,dense rank,queries of joins etc.
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Q2. Java 8 related ques optional and stream
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Q1. How to optimise fetching 1 lakh entries from db
Ans. 
Use pagination, indexing, caching, and query optimization to fetch 1 lakh entries efficiently from the database.
• Implement pagination to fetch data in smaller chunks

• Create indexes on columns frequently used in queries

• Use caching to store frequently accessed data

• Optimize queries by avoiding unnecessary joins and using appropriate indexes

• Consider using database-specific optimizations like query hints or stored procedures
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Q1. Reverse a linked list.
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Q2. Merge sort on a array/
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Q1. Memory management in java 8
Ans. 
Java 8 introduced improvements in memory management with features like Metaspace and G1 garbage collector.
• Java 8 introduced Metaspace to replace the PermGen space for class metadata storage.

• G1 garbage collector in Java 8 improves garbage collection performance by dividing the heap into regions.

• Java 8 also introduced the concept of String deduplication to reduce memory usage for String objects.
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Q2. CQRS pattern in microservices
Ans. 
CQRS pattern separates read and write operations in microservices for better scalability and performance.
• CQRS stands for Command Query Responsibility Segregation

• It separates the read and write operations in microservices

• Write operations update the data, while read operations retrieve the data

• Helps in improving scalability and performance by optimizing for each operation type
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Prepare for aptitude Test

Prepare for Data structures and Algorithm

Based on python and also question included networking

Q1. How to pull the large amount of data in spring data jpa
Ans. 
To pull large amount of data in Spring Data JPA, use pagination, lazy loading, and query optimization techniques.
• Use pagination to limit the amount of data retrieved in each query

• Implement lazy loading to fetch data only when needed

• Optimize queries by using indexes, avoiding N+1 query problem, and fetching only necessary columns
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Q2. Write singleton class
Ans. 
Singleton class ensures only one instance of a class is created and provides a global point of access to it.
• Create a private static instance of the class

• Provide a private constructor to prevent instantiation

• Create a public static method to access the instance
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Test had 2 sections..first section had 3 subsections with quants,verbal and logicals.2nd section is an English writing skill round where they give u a topic and u have to write ur views on it more than 200 words

Gd has the basic rules..they give a topic and u have to discuss on that

Q1. Hr asks you questions on your project,the programming language ur strong in and may be few code solving questions
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Q1. HR round tests your flexibility and adaptability skills.
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