10+ NeoSOFT Java Developer Interview Questions and Answers

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 communication between services.

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 (XSS)

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 the necessary methods or functionality.

• It is important to ...read more

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

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

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 b to x

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.

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 caching, request collapsing, and thread isolation.

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 for CRUD operations.

• JPA also provides features like cachi...read more

ArrayList is implemented as a resizable array, while LinkedList is implemented as a doubly linked list.

• ArrayList provides fast random access and slower insertion/deletion, while LinkedList provides fast insertion/deletion and slower random access.

• ArrayList uses less memory overhead compared to LinkedList.

• Example: ArrayList is more suitable for scenarios where frequent access and traversal of elements is required, while LinkedList is more suitable for scenarios where frequent ...read more

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 tables.

• Popular Java ORM tools include Hibernate, JPA (Java P...read more

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.

• Rest controller is lightweight and faster than Controller...read more

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.

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 corruption.

• It is open-source and has a large community for suppor...read more

HashSet is an unordered collection while TreeSet is a sorted collection.

• HashSet uses hashing to store elements, allowing for constant time complexity for basic operations like add, remove, and contains.

• TreeSet uses a Red-Black tree to store elements in sorted order, allowing for log(n) time complexity for basic operations.

• HashSet does not maintain any order of elements while TreeSet maintains elements in sorted order.

• HashSet does not allow duplicate elements while TreeSet doe...read more

Final, finally, and finalize have different meanings in Java.

• final is a keyword used to declare constants or prevent inheritance

• finally is a block used in exception handling to execute code after try/catch

• finalize is a method used for cleanup operations before an object is garbage collected

HashMap is not thread-safe, while ConcurrentHashMap is thread-safe.

• HashMap is not synchronized and not thread-safe, while ConcurrentHashMap is thread-safe.

• ConcurrentHashMap allows concurrent modifications without causing any ConcurrentModificationException.

• ConcurrentHashMap achieves thread-safety by dividing the map into segments, each with its own lock.