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Difference between HashMap vs IdentityHashMap in Java? Example

The IdentityHashMap is one of the lesser known Map implementations from JDK. Unlike general purposes Map implementations like HashMap and LinkedHashMap, it is very special and its internal working is quite different than HashMap. The main difference between IdentityHashMap and HashMap in Java is that the former uses the equality operator (==) instead of the equals() method to compare keys. This means you need the same key object to retrieve the value from IdentityHashMap, you cannot retrieve values by using another key that is logically equal to the previous key. 

How and When to use TreeMap in Java? Example Tutorial

Hello guys, I hope you all are doing well and having lots of fun reading and learning Java Collections together. Today we are here a meet again on our journey of Java. I hope you all have seatbelts buckled up as today it's gonna be an adventurous ride while learning something that is most used in many production applications, coding, and whatnot. Today's topic, TreeMap in Java is very important because it holds a very significant feature Java development kit provides. This is also one class which many Java developer doesn't pay attention but it is really used for many use cases. Most Java developer just keep their attention to ArrayList, HashSet, and HashMap and thus missing out on many cool Java collection classes like TreeMap, WeakHashMap, and LinkedHashMap which saw earlier.

How to delete multiple elements from a LinkedList in Java? SubList() Example

Hello guys, if you are looking for an easy way to remove a sub set of elements from a LinkedList in Java then you have come to the right place. In the past, I have shown you how to sort a LinkedList in Java and how to create your own linked list implementation in Java and in this article, I am going to introduce you with an interesting method which can be used to delete a portion of LinkedList in Java in shot. Yes, there is a method exists  but not many Java developer knows about it. The method is called subList() and you can use this method with clear method in Java to delete a portion of linked list in one shot.

How to use WeakHashMap in Java? Example Tutorial

Hello friends, we are here today again on our journey to Java. I hope everyone is fine and ready to board our train of knowledge. Today we are gonna learn something very interesting and very exciting. Today's topic will definitely be very useful in coding and programming. This topic would surely decrease your time complexity, and space requirements for any task very significantly :p So what's the wait? Let's start!

Top 20 Shell Scripting Interview Questions and Answers

Have you struggle with Shell Scripting interview questions before? Have you been having problems in finding out the kind of questions asked in a Shell Scripting interview? If you have experienced this then it is high time that you find a solution. You cannot lose that dream job anymore and yet you can find with ease all you require to pass your interview. If that interview is a few days away, worry no more because you will get before that panel fully prepared and ready for the day. 

Difference between HashMap vs TreeMap vs LinkedHashMap in Java

Hello guys, if you are wondering when to use HashMap, TreeMap and LinkedHashMap in Java and want to understand difference between them then you are at the right place. Earlier, I have shared difference between HashSet, TreeSet, and LinkedHashSet and in this article, I will explain the difference between these three common Map implementation HashMsp, TreeMap, and LinkedHashMap. Though all three classes like HashMap, LinkedHashMap and TreeMap are implementation of java.util.Map interface, there is some functional difference between them. Perhaps most notable difference between them comes from their iteration order. HashMap makes absolute no guarantee about in which order you can iterate their keys, any application depending upon iteration order of HashMap is fragile, because it can change anytime. In fact, in Java 7, iteration order of HashMap is different than Java 6. 

How to send Email in Java + Spring Framework? JavaMailSenderImpl Example Tutorial

Hello guys, if you are looking for a Java + Spring tutorial to send emails then you have come to the right place. Earlier, I have shared the free spring framework online courses, and today, I am going to share how to send Emails in the Java application using Spring and JavaMailSenderImpl class which makes it really easy to send emails from Java application.  Email is an essential function of any enterprise Java application. Your application will need Email functionality to send reminders, bills, payments, confirmations, passwords, alerts, and several other kinds of system notifications.

How to set the logging level in Spring Boot application.properties - Example Tutorial

Hello guys, if you are wondering how to set the logging level on spring boot then you have come to the right place. In the past, I have shared the best Spring Boot courses and free courses to learn Spring MVC and in this article, I will share how to set logging levels like DEBUG and INFO in Spring Boot.  How do we configure the logging level of our Spring boot application is one of the questions that arise when developing a large application. Because we need to trace errors, warnings, informational data when running our application and to this, Spring has introduced Spring boot logging configurations. 

Top 20 UI and UX Design Interview Questions and Answers

Hello folks, if you are a fresher who want to start your career in UI and UX design or a UI or UX Designer and preparing for your next job and looking for popular UI/UX  interview questions for preparation then you have come to the right place. Earlier, I have shared HTML Interview Question, CSS Interview Questions, web development questions, and JavaScript Interview Questions and in this article, I am going to share common UI and UX interview questions with answers. If you have worked in UI and UX design for quite sometime then you may know the answers of these questions but if you are new then you may need to go through these best UI and UX design courses to refresh you knowledge about essential UI and UX design concepts. 

Spring Boot + Thymyleaf Project in Java? Example Tutorial

Hello guys, if you are looking for a Spring Boot and Thymyleaf example, tutorial, or a project then you have come to the right place. Thymyleaf is one of the most popular, modern, server-side Java template engine to generate HTML and XHTML content. Earlier, I have shared Spring Boot + Reactjs project, as well a complete project to create Spring Boot + REST and Spring Boot + Microservices and in this tutorial, you will learn about how to create a spring boot and thyme leaf application using the h2 database.  So before moving to an example, let's discuss what is thymyleaf? Thymeleaf is a web application development library based on Java. It offers excellent support for providing XHTML/HTML5 in web applications.

How to use @ResponseBody and @RequestBody in Spring MVC and REST? Example Tutorial

Hello guys, if you are wondering what is @RequestBody and @ResponseBody annotation in Spring MVC and Spring Boot then you have come to the right place. Earlier, I have told you about the @RestController annotation and in this article, I am going to explain to you what is RequestBody and ResponseBody annotation, how to use them, and when to use them with simple examples. While working with REST API, we may need to bind HTTP requests and response bodies with the domain object. To bind this, we use we can use the @ResponseBody and @RequestBody annotations in Spring MVC. 

Top 20 YAML Interview Questions Answer for Developers and DevOps

Hello guys, if you don't know YAML stands for Yet Another Markup Language and its one of the popular language for defining system rules. YAML is used in Spring Integration and most popularly in Ansible for defining Ansible playbook which you can use to install or uninstall application and do other stuff. Because of that reasons YAML has become quite popular and you may be asked about basic questions in YAML if you are going for a Developer or DevOps Interview where YAML skills are required. At the very minimum you should know how to read YAML and how to write YAML, particular declaring list and key-value pair in YAML. It's not a big topic but knowing basic really help during interview.

How to test a Spring Boot application in Java? @SpringBootTest Example

Hello guys, if you are wondering how to test your Java + Spring Boot application then you are at the right place. Earlier, I have shared best Spring Boot Courses and Spring Boot + Microservice example and in this article, I will talk about how to test your Spring boot application, mainly about writing unit test and integration test for Java and Spring boot application. Unit testing and Integration testing are two skills which separates a normal developer from a professional Java developer and when it comes to testing Spring applications many Java developer doesn't really know how to do that. If you are new to Java and Spring development but keen to learn Unit testing both Java and Spring Boot application then you have come to the right place.

Java + Spring Boot + Microservices Example - Step by Step Guide

Hello guys, if you are wondering how to create a Microservice in Java and Spring Boot then you are ar the right place. In the past, I have shared best Spring Boot courses for Microservices, Interview Questions as well as essential Microservice design principles and patterns like circuit breaker, CQRS, Event sourcing etc and In this article, we will cover the fundamentals of microservices with Spring Boot utilizing Spring cloud. We will cover a few fundamental ideas and then we will make a little micro-service to give you an outline. I will also share step by step guide to make Microservices in Java and then deploy them using Docker and Kubernetes on Cloud. 

How to Find Lowest Common Ancestor of a Binary Tree in Java? Example Tutorial

Hello guys, if you are wondering how to find the lowest common ancestor of a binary tree in Java then you are at the right place. Earlier, I have shared 40+ binary tree questions and today I am going to share solution of one of the popular binary tree question here. To find the lowest common ancestor of a binary tree in java requires that we run through a binary search tree and how it operates.  What then is a binary search tree? A Binary tree is a data structure in which each node can have at most two children. That is, each node in the binary tree will have data, left child and right child. The first node of the tree is called the Root.

How to Enable Disable Spring Security in Spring Boot? Example Tutorial

Hello guys, if you are wondering how to enable and disable Spring Security in a Spring Boot based Java application then you have come to the right place. In the past, I have shared best Spring security courses25 Spring Security questions, as well multiple Spring security tutorials like how to use HTTP Basic auth in Spring Security etc.  and in this article, I will share multiple ways to enable and disable Spring Security in a Spring boot application. But, before that, if you are new to Spring Security then find out what is Spring Security and how does it work?  At its core, Spring Security is simply a bunch of servlet filters that assist you with adding authentication and authorization to your web application. 

Difference between Binary Tree, Binary Search Tree (BST), and Balanced Tree (AVL and Red Black Tree)?

Hello guys, if you are preparing for technical interview for Software Development job then you must prepare well for Data Structure and Algorithms. It is often the difference between selection and non-selection and when it comes to Data Structure, binary search tree is one of the tough topic to master. In the past, I have shared 100+ data structure questions and 40+ binary tree questions and today, I am going to share one of the popular theory or concept questions related to binary tree data structure.  The Tree data structure is one of the essential data structures, but unfortunately, many programmers don't pay enough attention to learning Trees, particularly advanced tree data structures like balanced trees like AVL and Red-Black tree. 

How to set base URL for REST in Spring Boot? Example Tutorial

Hello guys, if you are wondering how to set base URL for REST API in Spring Boot then you have come to the right place. Earlier, I have shared best REST API Courses for Java developers, REST API Books,  and a complete guide to create RESTful Web service using Spring Boot, in this article, I will show you how to set a base URL in any spring boot application? If you don't know what is a base URL in a REST application or website, let me give you a brief overview first.  A base URL is the continuous element of your REST API or website's address. For example, you'll notice that the address portion http://twitter.com displays in the address bar whenever you log on to your Twitter account or visit a Twitter profile from your computer. This is the primary or base URL.

How to Find/Print Leaf nodes in a Binary Tree in Java without Recursion - Example

In the last article, you have learned how to print all leaf nodes of a binary tree in Java by using Recursion, a useful technique to solve binary tree problems and in this article, we'll answer the same question without using Recursion. Why should we do this? Well, it's a typical pattern on a programming job interview to solve the same problem using both Recursion and Iteration. Since some questions are easy to solve using recursion like linked list problems, binary tree-based problems, tower of Hanoi, or Fibonacci series but their non-recursive solution is comparatively tricky, the interviewer tests candidates against this shift in the algorithm.

Top 50 Core Java Interview Questions and Answers for Beginners

Hello guys, If you are preparing for your next Core Java interview and looking for some common questions to practice or check your knowledge, then you have come to the right place. In this article, I'll share 50 Core Java Interview Questions from various companies. I have already discussed the answers to these questions in this blog or Javarevisited, so I have just put the link and given hint or mentioned the key point you need to know to answer these questions. First, you should try to answer it yourself, and if you cannot then go to the link and find the answer. You can also compare your answer with mine and learn a few things here and there.

Top 20 Linux and SQL Interview Questions for Java and IT Professionals

Hello guys, If you have worked as a software developer or Java programmer then you know that SQL, Linux, and Networking fundamentals are essential skills for any Java developer, especially for server-side Java programmers. It actually doesn't matter whether you are applying for the job as a Java developer or C++ developer, Python developer or Ruby programmer, SQL and UNIX always have some role to play in your career. It's even essential for people who have less to do with programming like application support guys, business analysts, project managers, and subject matter experts.  Hence, it's imperative for any programmer or IT professional to prepare both SQL and UNIX well before going for any job interview.

Top 20 Ansible Interview Questions Answers for DevOps and Senior Developers

Hello guys, if you are preparing for DevOps or senior developer interview then you must pay attention to modern Software development and deployment tools like Docker, Kubernetes, Ansible, Chef and Salt, Puppet etc. Gone are the days where you can crack any Java Developer interview by just answer few core Java questions about HashMap and ConcurrentHashMap, nowadays a lot is expected from Java developers. There are coding round where you need to solve coding problems and then there are multiple rounds of phone and video interviews where you are asked all of kind questions about Java, Spring Boot, as well as essential tools like JUnit, Mockito, Docker, Kubernetes, Ansible etc. While focus could be different, depending upon your role, like for DevOps knowledge of Ansible is very much required for Developer only basic knowledge is good enough. 

21 Frequently Asked Java Interview Questions Answers for 2 to 3 Years Experienced Programmers

If you have been to a couple of Java interviews then you know that there are some questions that keep repeating like the difference between == and equals() method and many of its popular cousins like HashMap vs Hashtable, ArrayList vs LinkedList, the difference between equals() and hashCode(), or difference between Comparator and Comparable in Java. I call them frequently asked Java interview questions, and I suggest every Java developer make a list of them for their own reference and revision. I am sure many Java programmer already has such a list of questions handy if you don't have then this is a good time to find and make your own list, or if you are in rush then you can also buy my book Grokking the Java Interview, which contains many such questions. 

Top 53 Java Programs from Coding and Programming Interviews

Hello guys, if you are learning to code and programming, or preparing for a programming job interview and looking for some practice material then you have come to the right place. Earlier, I have shared the best string, array, linked list, and binary tree coding problems and In this article, I am going to share some of the most common Java coding and programming problems for beginners. These are the problems, I have solved myself to learn to program and develop a coding sense and these are the ones that keep coming on Java coding interviews. By going through these coding problems you will not only learn Java but also prepare yourself for Java interviews. 

Top 50 Database and SQL Interview Questions Answers 1 to 5 Years Experienced

Hello guys, whether you are preparing for Java developer interview or any other Software Developer Interview, a DevOps Interview or a IT support interview, you should prepare for SQL and Database related questions. Along with Data Structure, Algorithms, System Design, and Computer Fundamentals, SQL and Database are two of the essential topic for programming or technical Job interview. In the past, I have shared many questions related to MSSQL questions, Oracle Questions, MySQL questions, and PostgreSQL questions and in this article, I am going to share both theory based and query based Database and SQL Interview questions with to the points answers.

Top 21 Git Interview Questions and Answers for Programmers and DevOps

Hello guys, if you are preparing for Software developer interview then you should prepare for Git, one of the essential and most popular version control and source control tool in Software industry. Almost every company, both big and small are now using Git to store their source code and conduct code reviews, yes the code review is one of the main reason many organization shifted to Git. Both Github and BitBucket provides in-built code review features which also promote good software development practices. 

Top 20 Agile and Scrum Interview Questions with Answers for 2 to 4 Years Experienced

Hello guys, ,if you are preparing for Software Developer interview then it makes to prepare questions on Agile and Scrum methodology. Agile is the standard way to develop software and most of the companies, both big and small follows Agile to develop and deliver Software. Before we get to the all-important interview questions that will help you land your dream software job, let me tell you something about Agile and Scrum. Agile Scrum is actually one of the best technologies out there today that will help you to implement accurate projects. Almost all of the major companies in the world use Agile these days. What that means for job hunters like you is that once you master this exciting technology, you will be able to position yourself really well in today's market.

Top 12 Servlet JSP Interview Questions for Java JEE Developers

Hello guys, Servlets and JSP Interview Questions are the core of any Java JEE Interview and why not they are the back bone of Java Web technology. While the industry have moved from JSP and JSF to React based frontend there are still millions of applications which are using JSP and Servlet in backend. They are also the underlying technology for any web framework on Java like Spring MVC or Spring Boot and It's expected from candidates to have good knowledge of Servlet, JSP, EJB, Struts, or Spring in any JEE interview. That's why Servlets and JSP Interview Questions are very common in any JEE Interviews along with some questions from core Java, Some interview Questions from Spring, and Some EJB interview questions

Top 20 Java Web Service Interview Questions with Answers

Java Web Services Questions and Answers
Web Services interview questions are part of J2EE interviews for jobs which are looking for some experience in Java web services Space. Most of the Web services questions come from two different ways of implementing Web Services like SOAP and REST. SOAP is standard and mature way of calling Web Services which uses XML while REST is a new way of implementing Web Services which is based on HTTP protocol. In fact REST Web Service interview questions are getting more and more popular on the web services interviews in Java, So if you are going for any Java J2EE interview which require some web service experience, be prepared with both SOAP and REST Web services questions.

Top 20 Jenkins Interview Questions Answers for Beginners and Experienced Developers

Hello guys, if you are preparing for Java developer interview or DevOps Interview, one tool which you should know well is Jenkins, the king of Continuous Integration and Continuous build, one of the most desirable skill companies look on experienced programmers now a days. Earlier, I have shared best free Jenkins courses for programmers to learn this useful tool as well as Interview questions on DevOps, Docker, and Kubernetes and in this article, I am going to share 20 frequently sked Jenkins and CI/CD Interview questions with answers for both beginners and experienced developers. 

Top 20 Selenium Interview Questions with Answers for Programmers and Testers

Hello guys, if you are preparing for Selenium Developer or Automation Testing Engineer interview and looking for frequently asked Selenium Interview Questions then you have come to the right place. Earlier, I have shared 130+ Core Java Interview Questions and 20 JUnit Interview Questions and in this article, I am going to share 20 common Selenium questions from interviews with answers. If you have worked with Selenium or used Selenium in your project then most likely you can answer all of these questions but if you struggle to answer any of these Selenium interview questions then you have always go back and check one of these best Selenium online course to learn and revise key Selenium concepts. 

Top 20 Python Programming Interview Questions with Answers for 1 to 2 Years Experienced

Hello guys, if you are preparing for Python developer interview and looking for common and frequently asked Python Interview Question then you have come to the right place. Earlier, I have shared best Python courses, books, and projects and today, I am going to share best Python Interview questions with answer to get you the Python developer job you always wanted. Understanding python is easy if you choose to. What is needed is more and more practice. In this article you will find the questions that are frequently asked during python interviews. You have to take your time and go through the questions with answers and you will be more than prepared as far as python interview is concerned. 

Top 27 Spring Security Interview Questions with Answers for 3 to 5 Years Experienced Java Developers

Hello guys, if you are preparing for Java and Spring Developer interview then you should prepare about Spring Security. Since Security is an important topic and Spring security is the most popular framework to implement security in Java web applications, there is always a few questions based upon Spring Security in Java developer interviews. In the past, I have shared Spring Boot questionsSpring Data JPA Question, Spring Cloud Questions, and Microservices Interview Questions and in this article, I will share 20 popular Spring security questions for practice. I have also shared answers so that you can revise key Spring security concepts quickly but if you think that you need more preparation on certain topic then you can also checkout this list of best Spring Security courses where I have shared online courses to learn Spring security in depth. 

Top 10 tools for SQL Developers and Database Administrators

 Hello guys, if you are a SQL database administrator a SQL Developer, a good knowledge of database tools can really help. It even been said that a craftsman is as good as his tools. So, you should spend some time and find out the tools which can help you with your job with respect to Database and SQL. Here are the main 10 free data set instruments that play out a great many explicit capabilities. The thought behind this rundown is to assist you with picking the right devices that best met your requirements.

10 Essential SQL Commands and Functions Every Developer should learn

Hello guys, if you are starting with SQL and wondering which commands you should learn first then you have come at the right place. In this article, I have shared 10 most essential SQL commands and functions which I believe every programmer should learn. This includes commands to pull data from database as well write data into data, update data, and remove data from database. While writing in the SQL language, you will utilize an assortment of SQL keywords to make explanations and questions. An assertion includes a series of characters and SQL keywords that adjusts to the designing and grammar rules of the language and may influence information or control processes corresponding to your information. 

Top 20 Kubernetes Interview Questions Answers for 1 to 3 Years Experienced

Hello guys, if you are preparing for Software developer or DevOps engineer Interview where Cloud Computing and Kubernetes skill are needed or mentioned in Job description then you should prepare for Kubernetes questions on Interviews. Kubernetes has quickly become an essential tool to deploy your application on Cloud and that's true not just for Java developers but also for Python, JavaScript, and Golang developers. If you already know the importance of Kubernetes and looking for common Kubernetes questions from interviews then you have come to the right place. Earlier, I have shared both Docker Interview questions and DevOps Interview Questions and in this article, I am going to share 20 common Kubernetes questions with answers.

How does Component Scanning works in Spring? @Configuration, @Component and @ComponentScan Example

Hello guys, if you are wondering how to does auto-wiring work in Spring Framework and how does Spring Framework find dependency in runtime then you have come to the right place. Earlier, I have explained How Spring MVC works and In this tutorial, I will tell you how component scanning and auto-wiring works in Spring. You will also learn how to enable component scanning in a Spring application. When you develop a software application using spring, you need to tell the Spring framework where to look for Spring components. Using component scanning it is very much easier as this enables auto-detection of beans by spring container and smoothly.

Top 15 HTML5 Interview Questions with Answers for 1 to 2 years Experienced

Hello guys, if you are preparing for web design or web development interview and looking for HTML 5 interview questions to revise key HTML 5 topics and concepts before interview then you have come to the right place. In the past, I have shared best HTML and CSS courses and in this article, I will share 15 common HTML 5 interview questions with answers for web design and web development interviews. You can use this list to quickly prepare for HTML 5 interviews. HTML is one of the three core technologies of the World Wide Web(WWW). It is the most essential part of a web application. Along with CSS and JavaScript, HTML is necessary to learn for web development. HTML is the easiest to learn and understand. 

13 Spring Boot Actuator Interview Questions Answers for 3 to 5 Years Experienced Java Developers

If you have used Spring Boot, you may know that Spring Boot is all about convenience, and the Spring Boot actuator is one of such features that provides a convenient way to interact with your app using HTTP and JMX. It's also essential from the Spring Boot interview point of view. While I did include some Spring Boot Actuator questions in my earlier post about frequently sked Spring boot interview questions, many of you asked for more questions to cover Spring Boot Actuator in depth, so I decided to write a separate article. In this article, we will see some popular Spring boot Actuator interview questions and, along the way, learn more about this helpful Spring boot Feature