Cognizant Java Spring Boot Developer Interview Questions and Answers

String is immutable, String Buffer is mutable.

• String is immutable, meaning its value cannot be changed once it is created.

• String Buffer is mutable, meaning its value can be changed after it is created.

• String is faster and more memory efficient for simple string operations.

• String Buffer is slower but more efficient for operations that require frequent modifications.

Dependency injection is a design pattern where the dependencies of a class are provided externally rather than being created within the class itself.

• Dependency injection helps in achieving loose coupling between classes.

• It allows for easier testing and maintenance of code.

• There are three types of dependency injection: constructor injection, setter injection, and interface injection.

• Example: In Spring Boot, dependencies

A singleton class is a class that allows only one instance of itself to be created and provides a global point of access to that instance.

• Singleton classes are often used in Spring Boot for managing resources such as database connections or thread pools.

• In Spring Boot, singleton beans are created by default, meaning that only one instance of a bean is created and shared across the application.

• To create a singleton bean...read more

HTTP status 204 means no content, while 404 means not found.

• HTTP status 204 indicates a successful request, but with no content to return.

• HTTP status 404 indicates that the requested resource could not be found on the server.

• HTTP status 204 is often used for successful DELETE requests where no content needs to be returned.

• HTTP status 404 is commonly seen when a user tries to access a non-existent URL.

Answers to common Java Spring Boot Developer interview questions.

• Java8 features include lambda expressions, functional interfaces, streams, and default methods.

• String is immutable in Java to ensure thread safety and prevent unintended modifications.

• Checked exceptions are checked at compile time, while unchecked exceptions are not. Example: IOException vs NullPointerException.

• throw is used to explicitly throw an excepti...read more

Spring is a framework for building Java applications, while Spring Boot is a tool for easily creating stand-alone, production-grade Spring-based applications.

• Spring is a framework that provides comprehensive infrastructure support for developing Java applications.

• Spring Boot is a tool that simplifies the process of creating and deploying Spring-based applications.

• Spring Boot includes embedded servers, which makes it ea...read more

Stateless API does not store client state on the server, while stateful API does.

• Stateless API: Each request from client to server must contain all necessary information for the server to fulfill the request. No client state is stored on the server. Example: RESTful APIs.

• Stateful API: The server stores client state, which can be accessed by subsequent requests. Example: HTTP sessions.