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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. 

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. 

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. 

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. 

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.

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 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.

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