HCL Group Java Developer Interview Questions and Answers

Interfaces in Java are implemented using the 'implements' keyword, allowing classes to provide specific implementations for methods defined in the interface.

• Interfaces in Java define a contract for classes to implement, specifying method signatures without implementations.

• A class can implement multiple interfaces by separating them with commas.

• Classes implementing an interface must provide concrete implementations for all methods defined in the interface.

• Interfaces can also c...read more

ArrayList is resizable array implementation, LinkedList is doubly linked list implementation.

• ArrayList uses dynamic array to store elements, LinkedList uses doubly linked list.

• ArrayList is faster for accessing elements by index, LinkedList is faster for adding/removing elements.

• Example: ArrayList arrList = new ArrayList<>(); LinkedList linkedList = new LinkedList<>();

throw is a keyword used to explicitly throw an exception, while Throwable is a class that serves as the base class for all exceptions in Java.

• throw is used to throw an exception in a method, while Throwable is the superclass of all exceptions in Java.

• throw is followed by an instance of Throwable class or its subclasses, while Throwable is a class that provides common methods for handling exceptions.

• Example: throw new NullPointerException(); - throws a NullPointerException

• Exam...read more

Spring Boot simplifies the setup and development of Spring applications by providing a convention-over-configuration approach.

• Spring Boot eliminates the need for XML configuration by using annotations and sensible defaults.

• It includes embedded servers like Tomcat, Jetty, or Undertow, making it easy to deploy standalone applications.

• Auto-configuration feature reduces the amount of boilerplate code needed to set up a Spring application.

• Actuator module provides production-ready ...read more

REST API is used to communicate between client and server using HTTP methods like GET, POST, PUT, DELETE.

• REST API allows clients to access and manipulate resources on a server using standard HTTP methods.

• It uses URLs to identify resources and HTTP methods to perform actions on those resources.

• Common HTTP methods used in REST API are GET (retrieve data), POST (create data), PUT (update data), DELETE (remove data).

• REST APIs typically return data in JSON or XML format.

• Authentica...read more

Stream API in Java provides a way to process collections of objects in a functional style.

• Stream API allows for functional-style operations on collections like map, filter, reduce, etc.

• It supports lazy evaluation, meaning operations are only performed when needed.

• Streams can be sequential or parallel, depending on the source and operations used.

Transactions in Spring Boot manage database operations as a single unit of work to ensure data integrity.

• Spring Boot provides support for declarative transaction management using @Transactional annotation.

• Transactions can be configured at class or method level.

• Transactions can be rolled back in case of exceptions to maintain data consistency.

• Example: @Transactional annotation on a service method ensures that all database operations within that method are part of a single tran...read more

Annotations in Spring Boot are used to provide metadata about the application and its components.

• Annotations are used to configure Spring Boot applications, define beans, handle requests, etc.

• Examples include @SpringBootApplication, @RestController, @Autowired, @RequestMapping, etc.