Fujitsu Senior Application Developer Interview Questions and Answers

Round duration - 60 Minutes
Round difficulty - Medium

This round started slow with some basic fundamental questions around OOPS and then paced up higher to some more advanced questions around Java 8 and Java in general.

Q1. Can you explain the SOLID principles in Object-Oriented Design?
Ans. 
SOLID principles are a set of five design principles in object-oriented programming to make software designs more understandable, flexible, and maintainable.
• S - Single Responsibility Principle: A class should have only one reason to change.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable...read more
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Q2. What is abstraction in Object-Oriented Programming?
Ans. 
Abstraction in OOP is the concept of hiding complex implementation details and showing only the necessary features of an object.
• Abstraction allows developers to focus on what an object does rather than how it does it

• It helps in reducing complexity and improving code reusability

• Example: In a car object, we only need to know how to drive it (interface) without worrying about the internal engine workings (implementation)
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Q3. How is an abstract class different from an interface?
Ans. 
Abstract class can have method implementations, while interface cannot.
• Abstract class can have method implementations, while interface cannot

• Abstract class can have constructors, while interface cannot

• A class can implement multiple interfaces, but can only inherit from one abstract class
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Q4. What is a classloader in Java?
Ans. 
A classloader in Java is a part of the Java Runtime Environment that dynamically loads Java classes into the Java Virtual Machine.
• Classloaders are responsible for loading classes at runtime based on the fully qualified name of the class.

• There are different types of classloaders in Java such as Bootstrap Classloader, Extension Classloader, and Application Classloader.

• Classloaders follow a delegation model where a classl...read more
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Q5. Why are Java Strings immutable in nature?
Ans. 
Java Strings are immutable to ensure data integrity, thread safety, and security.
• Immutable strings prevent accidental modification of data.

• String pool optimization is possible due to immutability.

• Thread safety is ensured as strings cannot be modified concurrently.

• Security is enhanced as sensitive information cannot be altered.
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Q6. Why is Java considered platform independent, while the Java Virtual Machine (JVM) is platform dependent?
Ans. 
Java code is compiled into bytecode which can run on any platform with JVM, making it platform independent. JVM itself is platform dependent as it needs to be installed on each platform to execute the bytecode.
• Java code is compiled into bytecode, which is a platform-independent intermediate code

• JVM interprets and executes the bytecode on different platforms

• JVM needs to be installed on each platform to run Java programs

• ...read more
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Q7. What are some standard Java pre-defined functional interfaces?
Ans. 
Standard Java pre-defined functional interfaces include Function, Consumer, Predicate, Supplier, etc.
• Function: Represents a function that accepts one argument and produces a result. Example: Function<Integer, String>

• Consumer: Represents an operation that accepts a single input argument and returns no result. Example: Consumer<String>

• Predicate: Represents a predicate (boolean-valued function) of one argument...read more
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Q8. What are the advantages of using the Optional class in Java?
Ans. 
Optional class in Java provides a way to handle null values more effectively.
• Prevents NullPointerException by explicitly checking for null values

• Encourages developers to handle null values properly

• Improves code readability and maintainability

• Helps avoid unnecessary null checks and nested if statements
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Round duration - 60 Minutes
Round difficulty - Medium

This round had questions from Microservices , Spring Boot and Hibernate. The interviewer was quite freindly and also helped
wherever I was stuck.

Q1. How many bean scopes are supported by Spring?
Ans. 
Spring supports five bean scopes: singleton, prototype, request, session, and application.
• Singleton scope: Default scope, only one instance per Spring container

• Prototype scope: New instance created each time bean is requested

• Request scope: Bean is created once per HTTP request

• Session scope: Bean is created once per HTTP session

• Application scope: Bean is created once per ServletContext
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Q2. What do you understand by autowiring in Spring Boot, and can you name the different modes of autowiring?
Ans. 
Autowiring in Spring Boot is a feature that allows Spring to automatically inject dependencies into a Spring bean.
• Autowiring eliminates the need for explicit bean wiring in the Spring configuration file.

• There are different modes of autowiring in Spring Boot: 'byName', 'byType', 'constructor', 'autodetect', and 'no'.

• For example, 'byName' autowiring matches and injects a bean based on the name of the bean property.
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Q3. Can you explain the @RestController annotation in Spring Boot?
Ans. 
The @RestController annotation in Spring Boot is used to define a class as a RESTful controller.
• Used to create RESTful web services in Spring Boot

• Combines @Controller and @ResponseBody annotations

• Eliminates the need to annotate each method with @ResponseBody
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Q4. What does the @SpringBootApplication annotation do internally?
Ans. 
The @SpringBootApplication annotation is used to mark a configuration class that declares one or more @Bean methods and also triggers auto-configuration and component scanning.
• Marks a class as a Spring Boot application

• Enables auto-configuration of the Spring application context

• Performs component scanning for Spring components

• Combines @Configuration, @EnableAutoConfiguration, and @ComponentScan annotations
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Q5. Can you explain the difference between setMaxResults() and setFetchSize() in a Query?
Ans. 
setMaxResults() limits the number of results returned by a query, while setFetchSize() determines the number of rows fetched at a time from the database.
• setMaxResults() is used to limit the number of results returned by a query.

• setFetchSize() determines the number of rows fetched at a time from the database.

• setMaxResults() is typically used for pagination purposes, while setFetchSize() can improve performance by reduci...read more
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Q6. What are the concurrency strategies available in Hibernate?
Ans. 
Hibernate provides several concurrency strategies like optimistic locking, pessimistic locking, and versioning.
• Optimistic locking: Allows multiple transactions to read and write to the database without locking the data. It checks for conflicts before committing the transaction.

• Pessimistic locking: Locks the data when a transaction reads it, preventing other transactions from accessing it until the lock is released.

• Vers...read more
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Q7. Can you explain the working of Microservice Architecture?
Ans. 
Microservice Architecture is an architectural style that structures an application as a collection of loosely coupled services.
• Microservices are small, independent services that work together to form a complete application.

• Each microservice is responsible for a specific business function and can be developed, deployed, and scaled independently.

• Communication between microservices is typically done through APIs.

• Microserv...read more
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Q8. What issues are generally addressed by Spring Cloud?
Ans. 
Spring Cloud addresses issues related to microservices architecture and cloud-native applications.
• Service discovery and registration

• Load balancing

• Circuit breakers

• Distributed messaging

• Configuration management

• Fault tolerance

• Monitoring and tracing
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Round duration - 30 Minutes
Round difficulty - Easy

This was a Technical Cum HR round where I was first asked some basic Java related concepts and then we discussed
about my expectations from the company , learnings and growth in the forthcomig years. I would suggest be honest and
try to communicate your thoughts properly in these type of rounds to maximise your chances of getting selected.