Infosys Interview Questions and Answers

Interfaces define a contract for classes to implement, while abstract classes can have both abstract and concrete methods.

• Interfaces can only have abstract methods and constants, while abstract classes can have both abstract and concrete methods.

• A class can implement multiple interfaces but can only inherit from one abstract class.

• Interfaces are used for achieving multiple inheritance in Java, while abstract classes are used to define a common behavior for subclasses.

• Interfac...read more

Object-oriented programming (OOP) is a programming paradigm based on the concept of objects, which can contain data in the form of fields and code in the form of procedures.

• OOP focuses on creating objects that interact with each other to solve problems

• It involves concepts like classes, objects, inheritance, polymorphism, and encapsulation

• Example: In a banking system, you can have classes like Account, Customer, and Transaction with their respective objects

String is a sequence of characters, while StringBuilder is a mutable sequence of characters used for manipulating strings efficiently.

• String is immutable in Java, meaning once created, it cannot be changed.

• StringBuilder is mutable and allows for efficient manipulation of strings.

• String concatenation using '+' operator creates a new string object each time, while StringBuilder's append method modifies the existing object.

• Use StringBuilder when frequent modifications to strings...read more

ASP.NET uses various validations like RequiredFieldValidator, RangeValidator, RegularExpressionValidator, etc.

• RequiredFieldValidator - Ensures a field is not left blank

• RangeValidator - Validates if a value falls within a specified range

• RegularExpressionValidator - Validates input based on a specified pattern

API stands for Application Programming Interface. It defines the methods and data formats that applications can use to communicate with each other.

• APIs can be classified into different types such as RESTful APIs, SOAP APIs, and GraphQL APIs.

• RESTful APIs use standard HTTP methods like GET, POST, PUT, DELETE to perform operations on resources.

• SOAP APIs use XML-based messaging protocol for communication between applications.

• GraphQL APIs allow clients to request only the data the...read more