FIS Senior Java Engineer Interview Questions and Answers

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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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. What are primitive and non primitive data types
Ans. 
Primitive data types are basic data types provided by the programming language, while non-primitive data types are created by the programmer.
• Primitive data types include int, float, double, char, boolean, etc.

• Non-primitive data types include arrays, classes, interfaces, etc.

• Primitive data types store actual values, while non-primitive data types store references to objects.
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Q2. What are access modifiers and non access modifiers
Ans. 
Access modifiers control the visibility of classes, methods, and variables. Non-access modifiers provide additional functionality.
• Access modifiers: public, private, protected, default

• Non-access modifiers: static, final, abstract, synchronized

• Example: public class MyClass { private int myVar; }
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Q3. What are all Java 8 features and explain the one which we have used in our project
Ans. 
Java 8 features include lambda expressions, functional interfaces, streams, and more.
• Lambda expressions allow concise syntax for defining anonymous functions.

• Functional interfaces can have only one abstract method and are used for lambda expressions.

• Streams provide a way to process collections of objects in a functional style.

• Optional class helps to avoid NullPointerException by wrapping a value that may be null.
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Q4. CICD tools which we have used explain in high level
Ans. 
CICD tools automate the process of building, testing, and deploying code changes.
• Popular CICD tools include Jenkins, GitLab CI/CD, CircleCI, and Travis CI

• These tools help in automating the software development lifecycle

• They enable continuous integration, continuous delivery, and continuous deployment

• CICD tools help in improving code quality, reducing manual errors, and increasing development speed
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Q5. What is containerization
Ans. 
Containerization is a lightweight, portable, and self-sufficient way to package and run applications.
• Containerization involves encapsulating an application and its dependencies into a container image.

• Containers are isolated from each other and share the host OS kernel.

• Popular containerization platforms include Docker and Kubernetes.

• Containerization allows for easy deployment and scaling of applications.
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Q6. What is indexing in sql
Ans. 
Indexing in SQL is a technique used to improve the performance of queries by creating a data structure that allows for faster retrieval of data.
• Indexes are created on columns in a database table to speed up the retrieval of rows that match a certain condition in a query.

• They work similar to the index in a book, allowing the database to quickly locate the rows that satisfy the query.

• Indexes can be created using a single...read more
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Q7. Programming question on stream like finding the longest string in a given list of string
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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

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Q1. Explain how hashmap internally works
Ans. 
HashMap internally uses an array of linked lists to store key-value pairs.
• HashMap uses hashing to determine the index of the key in the array.

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

• When retrieving a value, the key is hashed to find the index and then the linked list is searched for the key.
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Q2. Difference between vector and Arraylist
Ans. 
Vector is synchronized and slower, ArrayList is unsynchronized and faster.
• Vector is synchronized, ArrayList is not.

• Vector is slower due to synchronization, ArrayList is faster.

• Vector is legacy class, ArrayList is part of Java Collections framework.

• Vector doubles its size when full, ArrayList increases by 50%.
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Q1. No one showed up to interview
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Q2. Even they don’t responded to my mails
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They asked question about myself

Gave codeing in advance java concepts