If you have been developing REST APIs that are consumed by front end applications, it’s likely that you’ve come across this error, which is annoying for both frontend and backend developers. So let’s start with why we get this error? It’s because browsers don’t allow application from an origin to…

We can sort list using multiple fields with Comparator. Here we are going to see two ways to do that. Let’s say we have a Student class as below. public class Student { private int rollNum; private String firstName; private String stream; public Student(int rollNum, String firstName, String stream) { …

Java introduced Stream API in Java 8, which is useful to perform operations on collections. Java streams have definitely made processing collections and life easier. But in order to work with streams, it’s important to understand the following: Functional programming Functional Interface Lambda Expression Here I am going to explain…

Inheritance is an important concept of OOP. It allows inheriting fields and methods using ‘extends’ keyword. With inheritance, we can create a class with basic features and behaviors and create its specialized versions, by creating classes, that inherit this base class. The base class is also called superclass or parent…

The term exception is shorthand for the phrase “exceptional event.” Definition: An exception is an event, which occurs during the execution of a program, that disrupts the normal flow of the program’s instructions. When an error occurs within a method, the method creates an object and hands it off to…

Classes and objects are the fundamentals in java. Having a good understanding of how objects are created is essential for object oriented programming. new Operator new is a keyword in java that is used to create new object as the name suggests. What it does is allocate memory for the…