Ernst & Young Java Developer Interview Questions and Answers

Q1. They basically asked questions related to your project.
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Q2. Then asked design patters and related questions to it.
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Q3. Asked SOLID principal of software development.
Ans. 
SOLID principles are five design principles aimed at making software designs more understandable, flexible, and maintainable.
• S - Single Responsibility Principle: A class should have one reason to change. Example: A class handling user data should not also handle logging.

• O - Open/Closed Principle: Software entities should be open for extension but closed for modification. Example: Use interfaces to extend functionality ...read more
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Q4. Gave some coding questions related to Java array where I had to return the index of values whos total is 10.
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Q5. How you would connect springboot project with data base.
Ans. 
Use Spring Data JPA to connect Spring Boot project with database.
• Add database configuration in application.properties or application.yml file

• Create entity classes annotated with @Entity and @Table

• Create repository interfaces extending JpaRepository

• Use @Autowired annotation to inject repository in services or controllers
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Q1. DSA Collection Spring boot Java 8
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Q1. 1- REST API 2- MICROSERVICES 3- Java 4- DB
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Round duration - 60 Minutes
Round difficulty - Easy

This round started with some basic questions from Java followed by some questions from OOPS in Java and standard Java 8 questions.

Q1. What are the advantages of using Packages in Java?
Ans. 
Packages in Java help organize code, prevent naming conflicts, and provide access control.
• Organize code into logical groups for easier maintenance and readability

• Prevent naming conflicts by using unique package names

• Provide access control by using access modifiers like public, private, protected, and default

• Facilitate reusability by allowing classes to be easily imported and used in other packages
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Q2. Why is Java considered platform independent, while the Java Virtual Machine (JVM) is platform dependent?
Ans. 
Java is platform independent because it can run on any system with JVM, which is platform dependent due to its need to interact with the underlying hardware.
• Java code is compiled into bytecode, which can be executed on any system with a JVM installed.

• JVM acts as an intermediary between the Java code and the underlying hardware of the system.

• JVM is platform dependent because it needs to interact with the specific hardwa...read more
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Q3. Explain the use of the final keyword in a variable, method, and class.
Ans. 
The final keyword in Java is used to restrict the modification of variables, methods, and classes.
• Final variable: Once assigned, the value of a final variable cannot be changed.

• Final method: A final method cannot be overridden by subclasses.

• Final class: A final class cannot be extended.
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Q4. What is meant by an interface in Object-Oriented Programming?
Ans. 
An interface in OOP is a blueprint of a class that defines a set of methods without implementation.
• Interfaces in Java are used to achieve abstraction and multiple inheritance.

• All methods in an interface are abstract by default and do not have a body.

• Classes can implement multiple interfaces but can only extend one class.

• Example: interface Shape { void draw(); }

• Example: class Circle implements Shape { public void draw()...read more
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Q5. What is the difference between an abstract class and an interface in OOP?
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Abstract class can have both abstract and non-abstract methods, while interface can only have abstract methods.
• Abstract class can have constructors, fields, and methods, while interface can only have constants and method signatures.

• A class can extend only one abstract class, but can implement multiple interfaces.

• Abstract classes are used to define common characteristics of subclasses, while interfaces are used to defin...read more
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Q6. What are some standard Java pre-defined functional interfaces?
Ans. 
Some standard Java pre-defined functional interfaces include Function, Consumer, Predicate, and Supplier.
• 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 argu...read more
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Q7. What are the features of a lambda expression?
Ans. 
Lambda expressions are a feature introduced in Java 8 to provide a concise way to represent anonymous functions.
• Lambda expressions are used to provide implementation of a functional interface.

• They enable you to treat functionality as a method argument, or code as data.

• Syntax of lambda expressions is (argument) -> (body).

• Example: (int a, int b) -> a + b
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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. What are the basic annotations that Spring Boot offers?
Ans. 
Spring Boot offers annotations like @SpringBootApplication, @RestController, @Autowired, @Component, @RequestMapping, etc.
• @SpringBootApplication - Used to mark the main class of a Spring Boot application.

• @RestController - Used to define a class as a controller in a RESTful web service.

• @Autowired - Used for automatic dependency injection.

• @Component - Used to indicate that a class is a Spring component.

• @RequestMapping - ...read more
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Q2. 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 every method with @ResponseBody
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Q3. What is dependency injection?
Ans. 
Dependency injection is a design pattern in which the dependencies of an object are provided externally rather than created within the object itself.
• In dependency injection, the dependencies of a class are injected into the class from an external source, rather than the class creating the dependencies itself.

• This helps in achieving loose coupling between classes, making the code more maintainable and testable.

• There are...read more
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Q4. What does the @SpringBootApplication annotation do internally?
Ans. 
The @SpringBootApplication annotation is used to mark a class as a Spring Boot application and enables auto-configuration and component scanning.
• 1. Enables auto-configuration by scanning the classpath for specific types and configuring beans based on their presence.

• 2. Enables component scanning to automatically discover and register Spring components such as @Component, @Service, @Repository, and @Controller.

• 3. Combine...read more
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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 concurrent modifications before committing the transaction.

• Pessimistic locking: Locks the data to prevent other transactions from accessing or modifying it until the lock is released.

• Versi...read more
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Q7. Can you explain the N+1 SELECT problem in Hibernate?
Ans. 
N+1 SELECT problem in Hibernate occurs when a query results in N+1 additional queries being executed.
• Occurs when a query fetches a collection of entities and then for each entity, an additional query is executed to fetch related entities

• Can be resolved by using fetch joins or batch fetching to fetch all related entities in a single query

• Example: Fetching a list of orders and then for each order, fetching the customer i...read more
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Q8. 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.
• Each service is self-contained and can be developed, deployed, and scaled independently.

• Services communicate with each other over a network, typically using HTTP/REST or messaging protocols.

• Microservices allow for better scalability, flexibility, and resilience compared to monolithic architectu...read more
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Q9. What issues are generally addressed by Spring Cloud?
Ans. 
Spring Cloud addresses issues related to distributed systems and microservices architecture.
• Service discovery and registration

• Load balancing

• Circuit breakers

• Distributed configuration management

• Routing and gateway

• 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.