NielsenIQ Backend Java Developer Interview Questions and Answers

Q1. What improvements to interfaces were introduced in Java 8 that were missing in Java 7, specifically regarding static and default methods?
Ans. 
Java 8 introduced static and default methods in interfaces, allowing for method implementation and code reusability.
• Java 8 introduced static methods in interfaces, allowing for method implementation directly in the interface itself.

• Default methods were also introduced in Java 8, enabling interfaces to have method implementations without affecting implementing classes.

• Static methods in interfaces can be called using the...read more
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Q2. Explain internal working of HashMap ? How to synchronize it ?
Ans. 
HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.
• HashMap uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• To synchronize a HashMap, you can use the synchronizedMap() m...read more
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Q3. Given a list of employees with their ratings, how can you sort the employees based on their ratings using the Java 8 Streaming API?
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Q4. Will the program compile if the parent class throws a runtime exception while the child class throws an arithmetic exception?
Ans. 
No, the program will not compile if the parent class throws a runtime exception while the child class throws an arithmetic exception.
• In Java, if a parent class method throws a checked exception, the child class method can only throw the same exception or its subclasses.

• ArithmeticException is an unchecked exception, so if the parent class throws a checked exception and the child class throws an unchecked exception, the ...read more
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Q5. In a Spring Boot application with two databases, how can you configure JDBC to specify which database to use?
Ans. 
Configure JDBC in Spring Boot to specify which database to use
• Define multiple DataSource beans in the configuration class

• Use @Primary annotation to specify the primary DataSource

• Use @Qualifier annotation to specify the secondary DataSource

• Inject the DataSource beans where needed in the application
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Q6. How to use a jetty server in your spring boot application ?
Ans. 
To use a Jetty server in a Spring Boot application, you can configure it as a dependency and customize its settings.
• Add Jetty server dependency in your pom.xml file

• Exclude Tomcat server dependency if it's included by default in Spring Boot

• Configure Jetty server settings in application.properties or application.yml file

• Example: Add Jetty dependency - <dependency> <groupId>org.springframework.boot</groupId...read more
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Q7. Difference between @RequestParam and @PathVariable ?
Ans. 
RequestParam is used to extract query parameters from the URL, while PathVariable is used to extract values from the URI path.
• RequestParam is used for query parameters in the URL, while PathVariable is used for values in the URI path.

• RequestParam is optional, while PathVariable is required.

• RequestParam is used with the @RequestParam annotation, while PathVariable is used with the @PathVariable annotation.

• Example: @Requ...read more
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Q8. How would you handle a scenario where one microservice is awaiting a response from another microservice that is taking an extended time to respond?
Ans. 
I would implement timeout mechanisms and retries to handle the scenario of one microservice awaiting a response from another microservice taking an extended time.
• Implement timeout mechanisms in the calling microservice to limit the waiting time for a response.

• Set up retry logic to automatically resend the request to the slow microservice if no response is received within the specified timeout period.

• Use circuit breaker...read more
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Q1. Java 8 , java 11 and java 17 features?
Ans. 
Java 8 introduced lambda expressions, Java 11 added local-variable syntax for lambda parameters, and Java 17 included sealed classes and pattern matching.
• Java 8 introduced lambda expressions for functional programming.

• Java 11 added local-variable syntax for lambda parameters to simplify code.

• Java 17 included sealed classes to restrict inheritance and pattern matching for instanceof checks and type casts.
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Q2. Dispatcher servlet, design patterns
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Q3. @SpringbootApplication annotation, actuators
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Q4. String Coding question with java 8 features such as lambda function and stream api
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Q5. Number of words in a string
Ans. 
Count the number of words in a given string.
• Split the string by spaces and count the number of resulting elements.

• Handle edge cases like multiple spaces or empty strings.

• Consider punctuation marks as part of words unless specified otherwise.
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Q6. Microservice design patterns
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Q1. What are virtual threads and its uses
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Q2. Differenciate deep cloning vs shallow cloning with a code
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Onlin test consist pf easy numerical questions

Easy questions not so difficult

Q1. Java oops concept
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Q2. Basic sprophramming questions
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Q3. Networking firewall cisco
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Q1. Personal questions
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Q2. Whetehr to willing to work in any locations
Ans. 
Yes, I am willing to work in any location for the right opportunity.
• I am open to relocating for the right job opportunity

• I am flexible and adaptable to new environments

• I believe working in different locations can provide valuable experiences and growth opportunities
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Q1. What is Node Js
Ans. 
Node.js is a runtime environment that allows you to run JavaScript code outside of a web browser.
• Node.js is built on Chrome's V8 JavaScript engine.

• It uses an event-driven, non-blocking I/O model that makes it lightweight and efficient.

• Node.js is commonly used for building server-side applications and APIs.

• It has a large ecosystem of open-source libraries and frameworks, such as Express.js.
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Q2. What is middleware
Ans. 
Middleware is a software component that acts as a bridge between an application's request and response.
• Middleware functions have access to the request and response objects

• They can modify the request and response objects

• Middleware can be used for tasks like authentication, logging, error handling, etc.
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Q3. What is promise
Ans. 
A promise is an object representing the eventual completion or failure of an asynchronous operation.
• Promises are used to handle asynchronous operations in JavaScript.

• They can be in one of three states: pending, fulfilled, or rejected.

• Promises can be chained using .then() to handle success and .catch() to handle errors.

• Example: new Promise((resolve, reject) => { setTimeout(() => resolve('Done!'), 1000); });
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Q4. What is promise.all
Ans. 
promise.all is a method in JavaScript that takes an array of promises and returns a single promise that resolves when all of the input promises have resolved.
• Used to handle multiple asynchronous operations at once

• Returns a single promise that resolves when all input promises have resolved

• If any of the input promises is rejected, the returned promise is rejected with the reason of the first rejected promise
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Q5. What is callback
Ans. 
A callback is a function passed as an argument to another function to be executed later.
• Callbacks are commonly used in asynchronous programming to handle tasks that take time to complete.

• They are often used in event handling, timers, and AJAX requests.

• Callbacks can be synchronous or asynchronous, depending on when they are executed.

• Example: setTimeout(callback, 1000) will execute the callback function after 1 second.
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Q1. Circuit breaker pattern
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Q2. Aws S3 access via ECS
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Q1. Time Complexity
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Q2. Coding question and SQL queries
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