NTT Data Java Back End 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. Given an array {1, 2, 1, 4, 5, 4, 8, 7}, how can you use Streams to remove duplicates while retaining only the even numbers?
Ans. 
Use Streams to remove duplicates and retain only even numbers from an array.
• Convert the array to a stream using Arrays.stream()

• Use distinct() to remove duplicates

• Filter out odd numbers using filter()

• Collect the result using collect(Collectors.toList())
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Q2. What is the use of Static and final when you will use Static methods
Ans. 
Static methods can be accessed without creating an instance of the class, while final keyword makes the method unchangeable.
• Static methods belong to the class itself, not to any specific instance

• Final keyword ensures that the method cannot be overridden in subclasses

• Static methods are commonly used for utility methods that do not require access to instance variables

• Example: Math class in Java has static methods like Ma
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Q3. What is the difference between @restController and @controller Annotation
Ans. 
The @RestController annotation is used to define RESTful web services while @Controller annotation is used to define MVC controller.
• RestController is a specialized version of Controller used for RESTful web services

• RestController eliminates the need for @ResponseBody annotation

• Controller is used for traditional MVC controller functionality

• RestController returns data directly without needing to go through a view resolve...read more
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Q4. What is microservices why we use it
Ans. 
Microservices are a software development technique where applications are composed of small, independent services that communicate with each other.
• Microservices allow for easier scalability and maintenance of complex applications.

• Each service in a microservices architecture can be developed, deployed, and scaled independently.

• Microservices promote flexibility and agility in software development.

• Examples of companies us...read more
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Q1. Explain architecture of your project
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Q2. Some questions on Java, Spring Boot and sql
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Q1. Project flow and some behavioural questions
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Q2. Project contribution of yours
Ans. 
Developed a web application for tracking employee attendance and performance
• Implemented user authentication and authorization using Spring Security

• Utilized Hibernate for database interaction and data persistence

• Designed and developed RESTful APIs for frontend integration

• Used AngularJS for frontend development to create interactive user interfaces
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Q1. Basic formalities before offer release
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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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A standard online test conducted through one of the testing platforms.

Q1. Java 8 features
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Q2. Rest API
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Q3. Java 8 coding problem
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Q4. Collections
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Q1. It was based on my previous project
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Q1. What are microservices according to you?
Ans. 
Microservices are a software development technique where an application is divided into smaller, independent services that communicate with each other through APIs.
• Microservices are small, independent services that focus on specific business functions.

• Each microservice can be developed, deployed, and scaled independently.

• Microservices communicate with each other through APIs, typically using lightweight protocols like ...read more
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Q2. Explain Microservices Architecture used in your project
Ans. 
Microservices architecture is a design approach where a single application is composed of small, independent services that communicate with each other.
• Each microservice is responsible for a specific business function or capability

• Microservices communicate with each other through APIs

• Each microservice can be developed, deployed, and scaled independently

• Microservices architecture promotes flexibility, scalability, and re
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Q3. How are 4-5 microservices connected in rest api's? which technique you are using?
Ans. 
Microservices are connected in REST APIs using communication protocols like HTTP, messaging queues, and service discovery.
• Microservices communicate with each other using HTTP requests and responses.

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

• Service discovery tools like Eureka or Consul help in locating and connecting to different microservices.

• API Gateway ca...read more
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Q4. Coding question - 1. Create a immutable class of orders. What happens when two objects are created out of it. 2.Using the immutable orders create a set of orders and how will you sort these out. 3.Given ...read more
Ans. 
Creating immutable class of orders, sorting orders, finding average of lists of integers.
• Create an immutable class Orders with private final fields and no setter methods.

• Override equals() and hashCode() methods to ensure uniqueness of objects.

• Use Collections.unmodifiableSet() to create a set of orders and Collections.sort() to sort them.

• Iterate through the List of List of String of integers, convert to integers, and ca
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Q1. Explain Spring Cloud and how you are using in microservices?
Ans. 
Spring Cloud is a set of tools and frameworks for building cloud-native applications in Java.
• Spring Cloud provides tools for service discovery, load balancing, configuration management, and more in microservices architecture.

• It includes projects like Eureka for service discovery, Ribbon for client-side load balancing, and Config Server for externalized configuration.

• Spring Cloud integrates with Spring Boot to simplify ...read more
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Q2. Explain your deployment build config?
Ans. 
Deployment build config includes settings for deploying the application.
• Use tools like Maven or Gradle to manage dependencies and build the project

• Specify deployment environment configurations in a separate file (e.g. application.properties)

• Define build scripts for tasks like compiling, packaging, and deploying the application

• Leverage CI/CD pipelines for automated builds and deployments
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Q1. Explain your project?
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Q2. Your expectations from the company
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Given a project, you need to create logic for a service using helpers and finally give a aggregate of the final converted price .

Given few java 8 programming functions, you need to convert them to respective java 11 functions