10+ Cognizant Interview Questions and Answers

ActiveMQ is Java-based messaging broker while RabbitMQ is a message broker that implements the Advanced Message Queuing Protocol (AMQP).

• ActiveMQ is written in Java and supports multiple messaging protocols like OpenWire, STOMP, MQTT, and AMQP.

• RabbitMQ is written in Erlang and specifically implements the AMQP protocol.

• ActiveMQ is more feature-rich and has a larger user base, while RabbitMQ is known for its reliability and performance.

• ActiveMQ has a more complex setup and confi...read more

Azure DB offers various databases including SQL Database, Cosmos DB, MySQL, PostgreSQL, and MariaDB.

• SQL Database

• Cosmos DB

• MySQL

• PostgreSQL

• MariaDB

Singleton

• Default scope of a bean in Spring is singleton

• Singleton scope means that only one instance of the bean will be created for each Spring container

• This is the default scope in Spring, meaning if no scope is specified, the bean will be treated as a singleton

HashSet default size 16 for performance balance between memory usage and lookup time.

• Default size 16 provides a good balance between memory usage and lookup time.

• Choosing a power of 2 size helps in distributing elements evenly across buckets.

• Resizing the HashSet is expensive, so starting with a larger size reduces the need for resizing.

• Example: If the default size was too small, it would lead to more collisions and degrade performance.

Map and flatMap are methods in Java 8 Stream API used for transforming elements in a stream.

• Map applies a function to each element in the stream and returns a new stream with the transformed elements.

• FlatMap applies a function that returns a stream for each element in the original stream, then flattens the result into a single stream.

• Example: List words = Arrays.asList("hello", "world"); words.stream().map(String::toUpperCase).forEach(System.out::println);

• Example: List> numbe...read more

Microservices 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 lightweight protocols like HTTP or messaging queues.

• Microservices allow for flexibility, scalability, and easier maintenance compared to monolithic architectures.

• Examples of companies using microservices architecture inclu...read more

JUnit is a unit testing framework for Java, while Mockito is a mocking framework used for creating mock objects in unit tests.

• JUnit is used for writing and running repeatable automated tests to ensure code behaves as expected.

• Mockito is used to create mock objects to simulate the behavior of real objects in unit tests.

• Both JUnit and Mockito are commonly used in test-driven development (TDD) to ensure code quality and reliability.

HashSet is a collection of unique elements, while HashMap is a key-value pair collection.

• HashSet does not allow duplicate elements, HashMap allows duplicate keys but not duplicate values.

• HashSet uses Set interface, HashMap uses Map interface.

• Example: HashSet set = new HashSet<>(); HashMap map = new HashMap<>();

BDD stands for Behavior Driven Development and TDD stands for Test Driven Development.

• BDD focuses on the behavior of the system from the user's perspective.

• TDD focuses on writing tests before writing the actual code.

• BDD uses natural language to describe the behavior of the system.

• TDD helps in ensuring that the code meets the requirements and is well-tested.

• Both BDD and TDD help in improving the quality of the software and reducing bugs.

HashMap is a data structure that stores key-value pairs and uses hashing to quickly retrieve values based on keys.

• HashMap internally uses an array of linked lists to store key-value pairs.

• When a key-value pair is added, the key is hashed to determine the index in the array where it will be stored.

• If multiple keys hash to the same index, a linked list is used to handle collisions.

• HashMap allows null keys and values, and can have one null key and multiple null values.

• The load f...read more