We have heard the word “singleton” many time while working in java or being interviewed for the position in java development.

What is singleton class ?, Why is it being used ?, How to create singleton class in Java ? etc. These are the most common question being asked or comes to our mind while talking about singleton classes in java.

Thus this article is based on singleton class in Java and deep diving in this concept. We’ll move step by step. Lets get started.


As a Java developer, we are often being asked, what is the difference between Integer and int. We have used them many times while performing several numeric operations to meet the desired solution for business problems we are required to solve. The difference between them can be an another topic to discuss. For now we can understand that Integer is just a corresponding wrapper class for primitive datatype int. There are more such wrapper classes for different datatypes. A table consisting them is given below with this article. Also an interesting problem is given at the end. For understanding purpose…


As a developer we use various data structures to deal with different kind of data to meet certain requirements. We need to decide which data structure is best suited for our requirements.

Talking particularly for Java, we are provided with Collection of classes & interfaces which is popularly known as Collection framework. This has several useful classes & these classes have tons of methods which makes basic tasks super easy for developers. Collection Framework is a vast topic in itself. Here this article is just to give an inside view of arraylist, vectors, linkedlist, hashsets etc. …


FUNCTIONAL INTERFACE: A functional interface in Java is an interface consisting of a single abstract method in it. We either can use some functional interface provided by Java or create our own and use it as per our need.

Since these interfaces have only one abstract method, these are also called Single Abstract Method Interface (SAM). Though functional interface have only one abstract method, it can have multiple default, static methods in it. Java provides “@FunctionalInterface” annotation to declare interface as functional interface. Some of the commonly used Java functional interfaces are Runnable, Comparator, Callable etc.


Brief Introduction: GraphQL is a query language for APIs that allows clients to request limited data they need, making it possible for clients to gather data in a limited number of requests. One of the best thing we can have is a single end point for all the data we need from API.

GraphQL isn’t tied to any specific database or storage engine and is instead backed by our existing code and data. A GraphQL service is created by defining types and fields, then providing resolver methods for each field on each type.

Now let’s start by creating a springboot…

Vaibhav Gautam

Software engineer | Java developer | Angular | Student always

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