Shri Vile Parle Kelavani Mandal Interview Questions and Answers

OOPs concept in Java stands for Object-Oriented Programming, which focuses on creating objects that interact with each other.

• OOPs concept involves the use of classes and objects

• Encapsulation, Inheritance, Polymorphism, and Abstraction are key principles of OOPs

• Example: Creating a class 'Car' with properties like 'make', 'model', and methods like 'startEngine', 'drive'

Main method in Java is the entry point for any Java program. It is the method where the program starts execution.

• Main method must be declared as public, static, and void.

• It must accept an array of strings as an argument.

• It is the method where the program starts execution.

• Example: public static void main(String[] args) { }

A singleton is a design pattern that restricts the instantiation of a class to one object.

• Singleton pattern ensures that a class has only one instance and provides a global point of access to it.

• Commonly used in scenarios where only a single instance of a class is needed, such as database connections or logging.

• Implemented by creating a static method in the class that returns the same instance every time it is called.

Cross join is a type of join operation in SQL that returns the Cartesian product of two tables.

• Cross join combines each row from the first table with every row from the second table.

• It does not require any matching condition like other types of joins.

• Cross join can result in a large number of rows if the tables being joined have many rows.

• Example: SELECT * FROM table1 CROSS JOIN table2;

var is function scoped, let is block scoped in JavaScript

• var is function scoped, let is block scoped

• var can be redeclared, let cannot be redeclared

• let is recommended for variable declaration in modern JavaScript