Deutsche Telekom Senior Java Developer Interview Questions, Process, and Tips

Q1. Core Java knowledge check.
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Q1. Core java with Spring Boot and Microservice
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Q1. Project related questions
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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. What is different between Mysql Vs sql ?
Ans. 
MySQL is a specific implementation of SQL, which is a standardized language for managing databases.
• MySQL is a specific relational database management system (RDBMS) that uses SQL as its query language.

• SQL (Structured Query Language) is a standardized language for managing databases, used by various RDBMS like MySQL, Oracle, and SQL Server.

• MySQL is open-source and free to use, while some other RDBMS like Oracle may requ...read more
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Q2. What abstraction and interface in java?
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Abstraction and interface are key concepts in Java for achieving abstraction and defining contracts for classes.
• Abstraction in Java is achieved using abstract classes and interfaces.

• Abstract classes can have both abstract and concrete methods, while interfaces can only have abstract methods.

• Interfaces define contracts that classes must implement, allowing for polymorphism and loose coupling.

• Example: interface Shape { v...read more
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Q3. What is mean by JSP?
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JSP stands for JavaServer Pages, a technology used for creating dynamic web pages.
• JSP allows embedding Java code in HTML pages

• It simplifies the process of creating dynamic web content

• JSP files are compiled into servlets by the server for execution
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1st round some apt qns,some prgramming qns are they asked

Q1. C depth concepts and some prgram
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Q1. Some DSA questions they asked
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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. What are the things that u do when your what app screen is blank
Ans. 
I would check for internet connection, restart the app, clear cache, and update the app.
• Check internet connection

• Restart the app

• Clear cache

• Update the app
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Q2. Simple python code
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Q1. Memory management in java 8
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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
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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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