NTT Data Senior Java Developer Interview Questions and Answers

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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There were MCQ questions consists of different sections like Design Pattern,Java 8

Q1. Questions related to Multithreading,Design patterns
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Q2. Java coding questions
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Q1. Questions related to Multithreading
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Q2. Java coding questions
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Q1. Write a program on java8 ?
Ans. 
Program using Java 8 features to filter a list of strings starting with 'A' and convert them to uppercase.
• Use Java 8 stream API to filter the strings starting with 'A'.

• Use map() function to convert the filtered strings to uppercase.

• Collect the results into a new list using collect() function.
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Q2. How connect two dbs in spring boot?
Ans. 
To connect two databases in Spring Boot, you can configure multiple data sources and use JPA to interact with them.
• Configure multiple data sources in application.properties or application.yml file

• Define multiple DataSource beans in your configuration class

• Use @Primary annotation to specify the primary data source

• Use @Qualifier annotation to specify which data source to use in a specific repository or service

• Use @Transa...read more
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Q3. Index in MySQL?
Ans. 
An index in MySQL is a data structure that improves the speed of data retrieval operations on a database table.
• Indexes are used to quickly locate rows in a table without having to search every row.

• They can be created on one or more columns in a table.

• Indexes can be unique, which means that the indexed columns must contain unique values.

• Examples of indexes include primary keys, unique keys, and regular indexes.
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Q4. Difference between post & get mapping in spring boot and can we update the data using post mapping?
Ans. 
Post mapping is used to create or update data, while get mapping is used to retrieve data. Yes, data can be updated using post mapping.
• Post mapping is used to create or update data in the server, while get mapping is used to retrieve data from the server.

• Post mapping is typically used for operations that modify data, such as creating a new resource or updating an existing one.

• Get mapping is used for operations that do ...read more
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Q5. Microservices design patterns?
Ans. 
Design patterns in microservices architecture help in solving common problems and improving scalability, maintainability, and flexibility.
• Service Registry pattern - used for service discovery and registration, such as Netflix Eureka

• Circuit Breaker pattern - prevents cascading failures by failing fast and providing fallback mechanisms, like Hystrix

• API Gateway pattern - acts as a single entry point for clients to access ...read more
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Q6. Explain about SOLID principles in java?
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: Classes should be open for extension but closed for modification.

• L - Liskov Substitution Principle: Objects of a superclass should be replaceable with obje...read more
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Q7. What are the advantages of spring boot over spring?
Ans. 
Spring Boot simplifies the development of Spring applications by providing out-of-the-box configurations and reducing boilerplate code.
• Spring Boot provides a quick and easy way to set up a Spring application with minimal configuration.

• It includes embedded servers like Tomcat, Jetty, or Undertow, eliminating the need for deploying WAR files.

• Auto-configuration feature in Spring Boot automatically configures the applicati...read more
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Q8. Give one API task and need to sort the employee or users data based on the interviewer requirement?
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Q1. Java 8, exception handling for method overriding, collections basic on HashMap , hash set, blocking queue. Transient volatile
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Q1. Tell me about your self
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Q2. How garbage collection works in java
Ans. 
Garbage collection in Java is the process of automatically reclaiming memory by destroying unused objects.
• Garbage collection is performed by the JVM to free up memory occupied by objects that are no longer needed.

• It involves identifying and deleting objects that are no longer reachable by any part of the program.

• Java provides automatic garbage collection, so developers do not have to manually manage memory allocation a...read more
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Q3. Difference between String s = "xyz" and String s = new String("xyz")
Ans. 
The first statement creates a string literal in the string pool, while the second statement creates a new string object in the heap memory.
• String s = "xyz" creates a string literal in the string pool.

• String s = new String("xyz") creates a new string object in the heap memory.

• Using String s = new String("xyz") can lead to unnecessary memory usage.
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Q4. Difference between JVM JRE JDK
Ans. 
JVM is the virtual machine that runs Java programs, JRE is the runtime environment for Java programs, and JDK is the development kit for creating Java programs.
• JVM (Java Virtual Machine) is the virtual machine that runs Java bytecode and converts it into machine code.

• JRE (Java Runtime Environment) is the environment in which Java programs are executed. It includes JVM, libraries, and other necessary components.

• JDK (Jav...read more
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Q5. What is public static void main method
Ans. 
The public static void main method is the entry point of a Java program, where execution begins.
• It must be declared as public so that it can be accessed from outside the class.

• It must be declared as static so that it can be called without creating an instance of the class.

• It must have a return type of void, indicating that it does not return any value.

• It takes an array of strings (String[] args) as a parameter, which a...read more
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Q6. Difference between final finally finalize
Ans. 
final is a keyword used to declare constants, finally is a block used in exception handling, and finalize is a method used for cleanup.
• final keyword is used to declare constants that cannot be changed

• finally block is used in exception handling to ensure a piece of code is always executed

• finalize method is used for cleanup operations before an object is garbage collected
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Q7. Internal working of HashSet
Ans. 
HashSet is a collection class in Java that stores unique elements using a hash table.
• Uses hashing to store elements

• Does not maintain insertion order

• Allows null values

• Implements Set interface
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Q8. Hierarchy of ArrayList

Ans. 

ArrayList is a resizable array implementation in Java.

• ArrayList is a class in Java that implements the List interface.

• It allows dynamic resizing of the array, unlike regular arrays.

• Elements can be added, removed, or accessed using index.

• Example: ArrayList names = new ArrayList<>();

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