difference between class and objects ? what is method overloading and method overriding? define 4 concepts of oops ?abstraction inheritance polymorphism encapsulation write a program to calculate factorial of a number using recursion write a program to print second half of an array write a program to reverse a string without using for loop difference between selection sort and bubble sort write a query to create a table and insert elements in the table difference between sql and mysql how mongoDB works what is null pointer what is aws what is json anything you know about json define binary search //write a program to add digits a number primary key vs foreign key difference between call by value and call by reference