Digital Edge DC Interview Questions and Answers

This interview question covers various topics including abstract class, interface, HashMap, ArrayList, Linked List, String reversal, dependency injection, IOC container, and singleton class.

• Abstract class is a class that cannot be instantiated and can have both abstract and non-abstract methods.

• Interface is a blueprint of a class that can only have abstract methods and cannot be instantiated.

• HashMap is a data structure that stores key-value pairs and uses hashing to provide c...read more

Controller is a general term for handling requests, while Rest Controller is specifically for RESTful web services.

• Controller is responsible for handling incoming requests and returning responses.

• Rest Controller is a specialized type of controller that is used for building RESTful web services.

• Rest Controller uses HTTP methods like GET, POST, PUT, DELETE to perform CRUD operations on resources.

• Rest Controller returns data in JSON or XML format.

• Example: Spring MVC has a regula...read more

Stream API is a new feature in Java 8 that allows processing of collections in a functional way.

• Stream API provides a set of functional interfaces and methods to perform operations on collections.

• It supports parallel processing of collections, making it faster for large datasets.

• Examples of operations include filtering, mapping, sorting, and reducing.

• Stream API can be used with both primitive and object types.

• It promotes cleaner and more concise code compared to traditional l...read more

HashMap is a data structure that stores key-value pairs and uses hashing to efficiently retrieve values.

• 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.

• To retrieve a value, the key is hashed again to find the corresponding index and then the linked list is sea...read more

Optional class in Java is used to represent a value that may or may not be present.

• Optional class was introduced in Java 8.

• It is used to avoid null pointer exceptions.

• It can be used with streams to filter out null values.

• Example: Optional name = Optional.ofNullable(null);

• Example: Optional name = Optional.of("John");