Persistent Systems Java Developer Interview Questions and Answers

It's walkin, so they conducted 1 technical mcqs round.

Q1. Multi threading
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Q2. Internal working of hashmap
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Q3. Spring batch related
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Q4. Non repeating characters in a array
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Q5. 3rd highest salary
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Q6. Qualifier vs primary
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Q7. Controller vs restcontroller
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Q8. Spring boot annotataions
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Q9. Oops concepts with examples
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Q10. Spring batch configuration
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Q11. They covered all java, spring and Microservices
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Q1. Microservices architecture
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Q2. How do Microservices communicate
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Microservices communicate with each other through various communication protocols like HTTP, messaging queues, and gRPC.
• Microservices can communicate over HTTP using RESTful APIs.

• Messaging queues like RabbitMQ or Kafka can be used for asynchronous communication between microservices.

• gRPC is a high-performance, open-source RPC framework that can be used for communication between microservices.

• Service discovery mechanism...read more
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Q3. How to access the Microservice end point
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Q4. Why we use microservices
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Microservices allow for modular, scalable, and flexible software development by breaking down applications into smaller, independent services.
• Microservices enable easier maintenance and updates as each service can be developed, deployed, and scaled independently.

• They improve fault isolation, as failures in one service do not necessarily affect the entire application.

• Microservices promote agility and faster time-to-mark...read more
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Q1. Given an input string s ="aabbbcddbb". Write a java program to get output as a2b3c1d2b2
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Q2. Find 3rd highest from a list using streams api.
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Q1. Write a Rest api to get employee details by employee id.
Ans. 
A Rest api to get employee details by employee id
• Create a GET endpoint with a path like '/employees/{employeeId}'

• Retrieve employee details from a database using the employee id

• Return the employee details in JSON format
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Q2. Exceptional handling?
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Q1. How can distributed tracing be effectively handled in microservices?
Ans. 
Distributed tracing in microservices helps track requests across services for better performance and debugging.
• Use a tracing library like OpenTelemetry or Zipkin to instrument your services.

• Implement context propagation to pass trace IDs through service calls, e.g., using HTTP headers.

• Aggregate and visualize trace data using tools like Jaeger or Grafana for insights.

• Monitor latency and bottlenecks by analyzing trace da...read more
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Q2. What are the differences between Spring WebFlux and Spring MVC?
Ans. 
Spring WebFlux is a reactive programming framework, while Spring MVC is a traditional servlet-based framework for web applications.
• Reactive vs. Servlet: WebFlux is built on reactive programming principles, allowing for non-blocking I/O, while MVC is based on the servlet API and is blocking.

• Concurrency Model: WebFlux uses a reactive concurrency model with Project Reactor, enabling handling of many requests with fewer th...read more
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Q1. What is Custom exception?
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Q2. What is roles and responsibilities in your project?
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Q3. Find out duplicate element in array?
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