People Tech Group Java Developer Interview Questions and Answers

Q1. 1. How microservices communicate with each other?
Ans. 
Microservices communicate with each other through APIs and messaging protocols.
• Microservices use APIs to communicate with each other.

• Messaging protocols like HTTP, AMQP, and MQTT are used for asynchronous communication.

• Service discovery mechanisms like Eureka and Consul are used to locate services.

• API gateways like Zuul and Kong are used to manage API traffic.

• Event-driven architecture is used for real-time communicatio
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Q2. 2. How do you secure your APIs?
Ans. 
Securing APIs involves implementing authentication, authorization, encryption, and input validation.
• Implement authentication mechanisms like OAuth, JWT, or API keys

• Use authorization to control access to APIs based on user roles and permissions

• Encrypt sensitive data transmitted over the network using HTTPS

• Validate and sanitize input to prevent common security vulnerabilities like SQL injection or cross-site scripting (X
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Q3. 3. Scenario based question on qualifier?
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Q4. 4. What is ORM tool?
Ans. 
ORM (Object-Relational Mapping) tool is a software framework that maps objects to relational databases.
• ORM tool simplifies database operations by allowing developers to interact with databases using object-oriented programming.

• It eliminates the need for writing complex SQL queries by providing a higher-level abstraction.

• ORM tools handle tasks like data persistence, retrieval, and mapping between objects and database ta...read more
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Q5. 5. Advantages of hibernate
Ans. 
Hibernate simplifies database programming in Java applications.
• Hibernate provides a simple and efficient way to interact with databases.

• It eliminates the need for writing complex SQL queries.

• It supports object-oriented programming and mapping of Java classes to database tables.

• It provides caching and lazy loading mechanisms for improved performance.

• It supports transaction management and reduces the risk of data corrupt...read more
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Q6. 6. Rest controller vs Controller
Ans. 
Rest controller is used for RESTful web services while Controller is used for traditional web applications.
• Rest controller maps HTTP requests to RESTful web services while Controller maps HTTP requests to traditional web applications.

• Rest controller uses @RestController annotation while Controller uses @Controller annotation.

• Rest controller returns data in JSON or XML format while Controller returns data in HTML format...read more
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Q7. 7. What if i write component in place of service ?
Ans. 
Using component instead of service may cause confusion and errors in the code.
• Components and services are two different concepts in Java development.

• Components are used for UI elements while services are used for business logic.

• Using component instead of service may lead to errors in the code and confusion for other developers.

• For example, if a component is used instead of a service for business logic, it may not have ...read more
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Q8. 8. What is the work of @autowired?
Ans. 
The @Autowired annotation is used to automatically wire beans by matching the data type of the bean with the data type of the property.
• Used to inject dependencies automatically

• Reduces the need for manual bean configuration

• Can be used with constructors, fields, and methods

• Can be used with @Qualifier to specify which bean to wire
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Q9. 9. What is Eureka server ? Default port
Ans. 
Eureka server is a service registry that enables microservices to discover and communicate with each other.
• Eureka server is a component of Netflix's OSS suite.

• It allows services to register themselves and discover other services.

• It uses a REST API for communication.

• Default port is 8761.
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Q10. 10. What is circuit breaker? Hystrix
Ans. 
Circuit breaker is a design pattern used to prevent cascading failures in distributed systems. Hystrix is a popular implementation.
• Circuit breaker monitors the availability of a service and trips if the service fails repeatedly.

• It helps to prevent cascading failures by failing fast and providing fallback options.

• Hystrix is a popular implementation of circuit breaker pattern in Java.

• It provides features like request cac
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Q11. 11. What are ternary operators ?
Ans. 
Ternary operators are conditional operators that evaluate a boolean expression and return one of two values based on the result.
• Ternary operators are written in the form of 'condition ? value1 : value2'

• If the condition is true, the operator returns value1, otherwise it returns value2

• Ternary operators can be used as a shorthand for if-else statements

• Example: int x = (a > b) ? a : b; // assigns the larger value of a and
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Q12. 12. How to write the entity class?
Ans. 
Entity class represents a table in a database and its attributes as fields.
• Define class with @Entity annotation

• Add @Id annotation to primary key field

• Add @Column annotation to map fields to table columns

• Implement getters and setters

• Override equals() and hashCode() methods
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Q13. 13. What is crud vs Jpa ?
Ans. 
CRUD is a basic operation for data manipulation while JPA is a Java specification for ORM.
• CRUD stands for Create, Read, Update, and Delete which are basic operations for data manipulation.

• JPA is a Java specification for Object-Relational Mapping (ORM) which provides a way to map Java objects to relational database tables.

• JPA provides a higher level of abstraction and simplifies the data access layer by providing an API...read more
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Q1. What is Functional interface
Ans. 
Functional interface is an interface with only one abstract method, used for lambda expressions.
• Functional interfaces can have multiple default or static methods, but only one abstract method.

• They are used for lambda expressions and method references in Java.

• Examples of functional interfaces in Java include Runnable, Callable, and Comparator.
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Q2. Java 8 features
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Q3. One Coding question based on String
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Around 75 mcq questions with snippets of code

Q1. Interview conducted by technical lead. Around 10-15 questions asked. Questions related to your skills only.
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Q2. Basics of core java
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Q3. SQL queries, scenario based questions
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Q1. Daily routine. Casual question/non technical questions. Tricky question. Puzzles. Sone technical questions.
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Q1. What is oops concepts
Ans. 
Object-oriented programming concepts that help in organizing and structuring code.
• Encapsulation: Bundling data and methods together in a class.

• Inheritance: Creating new classes from existing ones, inheriting their properties and behaviors.

• Polymorphism: Objects of different classes can be treated as objects of a common superclass.

• Abstraction: Hiding complex implementation details and providing simplified interfaces.

• Enca...read more
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Q2. Abstraction polymorphism inheritance encapsulation
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I am good coder in java coding knowledge.

Q1. I am best technicaly in java .
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Q2. Base on java like core java .
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It was a 1 Hour aptitude test along a few MCQ based questions on DSA.

Q1. The interview was held online. The interview first asked me to explain any one of my projects.
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Q2. Asked a a few basic question of DSA like difference between quick and merge sort. Time complexities of a few algorithms. Real life application of Trees.
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Q3. A few basic questions related to OOPs
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Q4. Find missing numbers in a list in Python. (He asked me a few concepts related to Python since most of my projects were made in that)
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Q5. If A,B both classes have a function with same name (lets say the name of function id FUN) and C is a child of both. So, if FUN is called for C what will happen in Python and in C++.
Ans. Will give an error in C++, But will call FUN from whichever parent was declared first in Python
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Q6. He also asked me to implement quick sort
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