What is the delegating filter proxy in Spring Security? How it works?

The Delegating filter proxy or DelegatingFilterProxy is a spring aware class which implements javax.servlet.Filter interface and used to activate Spring security in a web application. Since Filters are created and maintained by Servlet or Web Container this filter is declared in web.xml and it is configured to process request for all URLs, which means every request and response pass through this filter. In other words, DelegatingFilterProxy works as a proxy between Web Container and Spring Container. It passes all request and response to Spring Security to implement security constraints e.g. performing authentication or authorization. 

5 Ways to Loop or Iterate over ArrayList in Java?

Looping over an ArrayList in Java or Iteration over ArrayList is very similar to a looping Map in Java. In order to loop ArrayList in Java, we can use either foreach loop, simple for loop, or Java Iterator from ArrayList. We have already touched iterating ArrayList in 10 Example of ArrayList in Java and we will see them here in more detail. We are going to see examples of all four approaches in this ArrayList tutorial and find out which one is clean and the best method of looping ArrayList in Java? But, before start writing an example for loop in ArrayList let's think about why do we need to iterate, traverse or loop an ArrayList if it’s based on the index and backed by Array.

How to get the selected radio button on click using jQuery? Example Tutorial

In last couple of articles, you have learned how to get all checked checkbox and how to find the unchecked checkbox using jQuery, let's see another similar example, this time with radio button. Suppose, in form you have two radio buttons to select the gender i.e. male and female. How do you find which radio button was selected when user clicked on them? well, we will use the jQuery selector to find that. In fact, its not much different than what you have used to find the checked checkbox i.e. $("input[type=radio]:checked") will give the selected radio button. In order to find the chosen radio button when user click, you need to bind a click handler.

10 Example of Hashtable in Java – Java Hashtable Tutorial

Hello Java programmers, if you are wondering how to use Hashtable class in Java then you have come to the right place. In this Java Hashtable tutorial, I am going to share how to use Hashtable in Java with examples. These Java Hashtable Examples contain some of the frequently used operations on Hashtable in Java. when I discussed throw of How HashMap or Hashtable works in Java I touched based on the inner working of Hashtable, while in this Java Hashtable tutorial we will see more examples of Hashtable in Java like checking a key exits in HashMap or not or get all keys and values from HashMap, Iterating on Hashtable keys and values using Enumeration, checking if Hashtable contains a particular key or value, how to copy mappings from a Hashtable to HashMap in Java, etc.

How to sort a Map by keys in Java 8 - Example Tutorial

Hello Java friends, In the last article, I have shown you how to sort a Map by values in Java 8, and in this tutorial, you will learn how to sort a Map by keys like a HashMap, ConcurrentHashMap, LinkedHashMap, or even Hashtable. Theoretically, you cannot sort a Map because it doesn't provide any ordering guarantee. For example, when you iterate over a HashMap, you don't know in which order entries will be traversed because HashMap doesn't provide any ordering. Then, how can you sort a Map which doesn't support order? Well, you can't and that's why you only sort entries of HashMap but you don't store the result back into HasMap or any other Map which doesn't support ordering. If you do so, then sorting will be lost.

Top 30 Array Interview Questions and Answers for Programmers

The array data structure is one of the most important topics for programming interviews. It doesn't matter if you are going to Google, Microsoft, Amazon or investment banks like Goldman Sachs, Barclays, Citi or even service-based companies like IBM, Accenture, TCS, or Infosys, if you are going to interview for the developer position, you must prepare array very well. In fact, it is the second most topic after String and if you look closely, may of String coding problems can be solved by treating them like character array. The array is also ubiquitous, no matter which programming language you choose, you will find array there, it's available in C, C++, Java and even on Python, Perl, and Ruby.

What is WeakHashMap in Java? When to use it? Example Tutorial

WeakHashMap is an implementation of Map interface in Java. It's a special Map where entries can be reclaimed by Garbage collector if there is no more strong reference exists to the value, apart from the key in the WeakHashMap, which is anyway the weak reference. This property allows a WeakHashMap to be used as Cache, where Garbage Collector can automatically cleanup dead entries. I mean those objects which are only alive inside map but there is no outside entries. Worth noting is that the key are stored as WeakReferences inside WeakHashMap which allows values to be reclaimed if there is no strong reference exists outside.

17 SQL Query Best Practices Every Developer Should Learn

Hello guys, its no secret that SQL is one of the must have skill in this data driven world and its also one of those skills which is equally useful for programmers, developers, database admins, data scientists, data analyst, business analyst, quality analyst and even project managers. I first learned SQL 20 years back when I was in college and that time we are using Oracle database. I still remember my first query about "SELECT * FROM EMP",  EMP was one of the tables which was quite popular among learners and most of the Oracle DB instance on labs have that. 

How to declare and initialize two dimensional Array in Java? Example Tutorial

There are many ways you can declare a two-dimensional integer array in Java. Since 2D array in Java is nothing but an array of array, you can even declare array with just one dimension, the first one; second dimension is optional. You can even declare a 2 dimensional array where each sub array has different lengths. You can also initialize the array at the time of declaration or on some later time by using nested for loop. So there is lots of flexibility. In this article, you will learn common Java idioms to declare and initialize two dimensional arrays with different lengths. 

What is lazy loading in Hibernate? Lazy vs Eager loading Example

Lazy loading in Hibernate is a feature which allows Hibernate to load the dependent objects lazily to improve performance of Java application. By default Hibernate does eager or aggressive loading for single valued associations (many to one and one-to-one ) and lazy loading for collection-valued associations (one to many or many-to-many). If you set the loading to lazy=false or FetchType.EAGER then object will be eagerly loader, means when an object is loaded from database all its relationship and associated objects are also loaded from Database e.g. when an Author entity object is initialized then all the books written by this author will also be loaded into memory.

Difference between @Secured vs @RolesAllowed vs @PreAuthorize, @PostAuthorize Annotations in Spring Security

Spring Security is a powerful framework to implement security on Spring based Java web application as well as on security RESTful Web Services. It also provides method level security, which means restricting access to a method depending upon role and permissions of object. If a user calling the method has access the method will be executed, otherwise AccessDeniedException will be thrown by Spring Security. All these annotations e.g. @Secured, @RolesAllowed, @PreAuthorize, and @PostAuthorize is used to implement method level security in Spring security, but there are some subtle difference between them. 

How to reverse an ArrayList in place in Java? Example [Solved]

How to reverse an ArrayList in place is a popular coding interview problem, not just on Java interviews but also for other programming language. I often ask to check whether candidate is familiar with in place algorithms or not.  You can reverse an ArrayList in place in Java by using the same algorithm we have used to reverse an array in place in Java. If you have already solved that problem then It's a no-brainer because ArrayList is nothing but a dynamic array, which can resize itself. All elements of an array are stored in the internal array itself. 

How to Remove Duplicates from Array without Using Java Collection API? Example

This is a coding question recently asked to one of my readers in a Java Technical interview on investment bank. The question was to remove duplicates from an integer array without using any collection API classes like Set, HashSet, TreeSet or LinkedHashSet, which can make this task trivial. In general, if you need to do this for any project work, I suggest better using the Set interface, particularly LinkedHashSet, because that also keeps the order on which elements are inserted into Set. Why Set? because it doesn't allow duplicates and if you insert duplicate the add() method of Set interface will return false. 

12 Apache HTTP Server Interview Questions Answers for 1 to 3 years Experienced

Hello guys, if you are preparing for Java web developer interviews then you must prepare questions on Apache HTTP web server, one of the most popular web server on internet. Knowing how Apache Web Server works not only shows that you have practical experience but also demonstrate your attitude about learning things in depth. The Apache HTTP Server, also known as httpd, has been the most popular web server on the Internet since April of 1996. It is both free and robust and that's the reason that almost half of the world's websites  runs on Apache HTTP web server, ranging from small hobby websites to huge e-commerce giants and big banks. 

17 Scenario Based Debugging Interview Questions for Experienced Java Programmers

If you are a beginner or an experienced Java developer with 1 to 3 years of experience under your belt, when you go for a Java interview you should prepare some Java troubleshooting and debugging interview questions like how to debug a Java program running in Linux environment? have you done remote debugging? have you ever profile your application? Your application is getting OutOfMemoryError, how are you going to find the root cause and fix? etc. These types of scenario based questions are quite popular while interviewing 5 to 10 years experienced Java developers to see their hands-on knowledge and find out they are rusty or not. 

10 Singleton Pattern Interview Questions in Java - Answered

Singleton design pattern is one of the most common patterns you will see in Java applications and it’s also used heavily in core Java libraries. Questions from the Singleton pattern are very common in Java interviews and good knowledge of how to implement the Singleton pattern certainly helps. This is also one of my favorite design pattern interview questions and has lots of interesting follow-ups to dig into details, this not only checks the knowledge of design pattern but also checks to code, multithreading aspect which is very important while working for a real-life application.

14 Multicasting Interview Questions and Answers

Hello guys, Multicasting is an important concept for Java developers, particularly those working on high frequency low latency Java application like trading apps, client connectivity and exchange connectivity systems, order management systems (OMS), Algorithm trading system, and smart order routers. As it provides a faster way to deliver messages than TCP. Yes, Multicasting is usually UDP based which is faster than TCP. While UDP doesn't guarantee message delivery, you can use things like sequence number to track messages and replay if a message went missing. Since multicasting is heavily used on big investment banks like JP Morgan, Barclays, Citi, Morgan Stanley, and others on their Java applications, its also an important topics for interviews. Not just on banks but also on many product based companies. 

Top 20 Algorithms Interview Problems for Programmers and Software Engineers

Hello All, If you are preparing for Programming job interviews or looking for a new job then you know that it's not an easy task. You got to be lucky to get a call from recruiter or hiring manager and make it to the first round of interview at any stage of your career but it is even more difficult at the beginner level when you are searching for your first job. That's why you can't just take your chance lightly. You got to be prepared to grab that chance and for that, you must know what is expected from you on the coding interview. What type of questions is asked, what topics should you prepare, etc? 

How HashMap works in Java?

Hello guys, if you are looking for an answer of popular Java interview question, how HashMap works in Java? or How HashMap works internally in Java then you have come to the right place. In this article, I will not just answer those question but also many related questions like How get() and put() method works in Java? what role equals() and hashcode() play in HashMap, How HashMap resize itself, and why key object of HashMap should be Immutable in Java. Let's start with the basics first. HashMap in Java works on hashing principles. It is a data structure that allows us to store object and retrieve it in constant time O(1) provided we know the key. Also this is one of my most popular article with more than 6 million views and I have now updated it to include latest information like how HashMap now uses a balanced tree instead of linked list for storing collision objects and new diagrams on HashMap working which provide visual explanations. 

Top 12 SQL Query Problems for Coding Interviews (with Solutions)

Hello guys, if you are looking for SQL query examples from interviews or SQL Query Practice questions to improve your SQL skill or just to prepare for tech interviews  then you have come to the right place. Earlier, I have shared best websites to learn SQL and Practice Query online and in this article, I am going to share 12 popular SQL query questions from interviews. SQL is an important skills for both programmers and data scientist, even people from QA and BA stream also need to know SQL to do their job well in this era or data driven world. That's why SQL queries are also quite popular on interviews. 

Top 50 Java Programs from Coding Interviews

Coding problems are an integral part of any programming job interviews, and Java development interviews are no exception. I would even suggest you should never hire anyone without testing their coding skill, but coding is also an art, and more often than a good coder is also an excellent developer. If you look at tech giants like Amazon, Facebook, and Google they thoroughly test the coding skill of any developer they hire, notably Amazon who first send online coding exercises to filter Java programmers who can code from those who can't code. This online test usually gives you requirements and ask you to write a program in a limited time, usually 2 to 3 hours. The application should meet the output provided by the exercise itself. These type of tasks are very tough to crack if you don't have excellent coding skill.

42 Programming Interview Questions for 1 to 3 Years Experienced Programmers (with Answers)

Hello guys, if you are preparing for programming job interviews and looking for previous asked questions or popular questions to get idea what topics are important for interviews then you have come to the right place. In the past, I have shared system design questions, SQL questions, UNIX questions and Java questions and in this article, I am going to share 42 programming interview questions for 1 to 3 years of experienced programmers. Though, its also useful for programmers up to 5 years of experience and we will start with programming questions from telephonic round of interviews. Due to COVID and work from home culture, in the last few years, phone interviews also known as the telephonic round has become the single most popular way to screen candidates in a programming job interview. It's easy for both parties to gauge each other, the candidate doesn't need to travel to the prospective Employer's premises and the Interviewer also doesn't need to make any unnecessary arrangements. 

How to Create a TCP Client and Server in Java? Example Tutorial

Hello guys, if you want to create client server application in Java then you need to learn Java networking API an classes like Socket and ServerSocket. In the past, I have showed you how to create an HTTP Client and Server in Java where I talked about these classes. In this Java networking tutorial, we will learn how to create a simple TCP server and Client in Java using networking classes provided by JDK in java.net package. Earlier, I have showed you how to create HTTP Server, which is actually a TCP/IP Server but here we'll do it again, along with writing a TCP client as well. Though you can test your TCP server using telnet, I'll show you how to connect to it using a TCP client written in Java. 

Top 5 SQL Server Tips for Beginners and Junior DBAs

Hello guys, If you are using Microsoft SQL Server database and use SQL Server Management Studio in your day to day work and looking for SQL Server tips to improve productivity and work fast and efficiently then you have come to the right place. Earlier, I have shared SQL Server online courses, SQL Server Interview questions and SQL Server Management Studio keyboard shortcuts and today, I am going to share amazing tips to make most of SSMS. These are the tips I learned hard way after working close to 8 years on SQL Server backend.

How to find smallest number from int array in Java, Python, JavaScript and Golang? [Solved]

This is the second part on this array interview question. In the first part, I have showed you how to find the largest element in array, and in this part, you will learn how to find the smallest number from an integer array. We will solve this problem on Java programming language but you are free to solve in any other programming language like Python or JavaScript. Most interviewer doesn't care much about which programming language you are solving the question, if you can provide working solution. This one is also a popular Java programming exercise which is taught in school and colleges and give in homework to teach programming to kids and engineering graduates. 

How to update an entity using Spring Data JPA ? Example Tutorial

Hello Java programmers and Spring Boot developers, if you are wondering how to update an entity using Spring Data JPA and looking for a tutorial or example then you have come to the right place. Earlier, I have shared the best Spring Boot courses and best Spring Data JPA Courses and in this article, I will show you how you can update any entry using Spring Data JPA?. How to update an entity using spring-data-JPA is also a  must-know topic when it comes to spring application development. Query methods are supported by Spring for updating operations. Entities are typically modified with Hibernate by retrieving them from the database, changing specific fields, and persisting the entities.

Top 15 NetBeans Keyboard Shortcuts for Java Programmers

In Java development there are three big IDEs, IntelliJ IDEA, Eclipse and NetBeans. In the past, I have shared Eclipse keyboard shortcuts and IntelliJ IDEA courses and today, I am going to share keyboard shortcuts for NetBeans, one of the first Java IDE I used in my career. I started doing Java development when JCreator was considered great because it can help with function names on objects but when NetBeans comes with features like built-in Tomcat and built-in profiler, it changed the game and I extensively used NetBeans for both web and mobile application development with J2ME. Since then a lot of water have flown in to Java world, InelliJIDEA become the defacto standard IDE for Java development with Eclipse as close second but unlike what many expected, NetBeans didn't die.

Review - Is System Design Interview - An Insider's Guide by Alex Xu and Shan Lam worth?

Hello guys, if you are preparing for System design interviews or Software Design Interviews, then you must have come across System Design Interview - An Insider's Guide by Alex Xu and Shan Lam, one of the most popular book on System Design after Designing Data-Intensive Applications by Martin Kleppmann. I first come across Alex Xu on Twitter when one of his image about how HTTPS works went viral. The image was quite detailed and presentable so I start following Alex and then I come across ByteByteGo, his online System design course and his book System Design Interview - An Insider's Guide. 

How to show and hide a div using jQuery? show(), hide(), and toggle() function Example

So, you have a div element and you want to show or hide them may be on a click or during page load, how do you do that in jQuery? Well, jQuery provides convenient show() and hide() methods which can show or hide an element, including div. All you need to do is, write a jQuery selector to find the div you want to show or hide and then call jQuery function show() or hide() depending upon your requirement. You can also use the toggle() function to switch between showing and hiding. This method will make element visible if its hidden and vice-versa. To select the div you can use either element, id or class selector but I recommend to use the ID selector because it will work even if you have multiple div in your page. 

How to version REST API? URL vs Header Versioning? Example Tutorial

Designing a real world, industry standard RESTful API can be a tricky challenge becuase there is no real standard exists. To add into that, there is also a lot of confusing topics e.g. PUT vs POST for creating and updating resources, or using URL or Header for versioning. There are a lot of advices you will find on internet often confusing and advocating one or other alternative, but it ultimately depends upon your own wisdom and use cases to come up with elegant RESTful URIs, which supports both filtering and versioning. There are both pros and cons of URL versioning and Hypermedia version, which we'll discuss in this article, but the most important lesson to learn is that you should always version your REST API. 

Top 20 Spring Boot Interview Questions with Answers for Java Developers

Hello Java developers, there is no doubt that the Spring Boot is now the standard way to develop Java application using Spring Framework, and that's why Spring Boot Questions are increasingly becoming popular on Java interviews. In the past, I have shared many Spring MVC interview questions in this blog like the @RestController vs. @Controller, but I haven't got a chance to share any questions on Spring Boot, Spring Cloud, and Microservices. After a couple of personal requests from my readers, I thought to write about, and here comes my list of top 20 Spring Boot interview questions for Java developers.

Top 50 Free Spring Certification Practice Questions Answers for Java Developers

Hello guys, if you are preparing for Spring Professional certification in 2024 and looking for free Practice questions then you have come to the right place. I have an excellent update to share with you from 5th April 2024 onward, you don't need to complete any mandatory training or Spring Pro courses to become eligible for Spring certification, its free like it was before VMware acquired and now you just need to buy voucher to give this exam.  Earlier, I have shared best spring books and courses and today, I am going to share 50+ spring boot practice questions for this certification. To be honest, preparing for IT certification like Oracle's Java certification or VMware's Spring Certification required a lot of hard-work. I have seen many experienced Java developers failing these certifications and losing money and time due to overconfidence and lack of preparation. 

Difference between Setter vs Constructor Injection in Spring

Spring Setter vs. Constructor Injection

Spring supports two types of dependency Injection, using a setter method, e.g. setXXX(), where XXX is a dependency or via a constructor argument. The first way of dependency injection is known as setter injection while later is known as constructor injection. Both approaches of Injecting dependency on Spring bean has there pros and cons, which we will see in this Spring framework article. The difference between Setter Injection and Constructor Injection in Spring is also a popular Spring framework interview question. 

How to sort a HashMap in Java 8 by keys and values using Stream and Lambda Expressions

Technically, you cannot sort a HashMap in Java because it doesn't guarantee any order. So, even if you add entries in sorted order they will be placed randomly and you won't be able to iterate over map in sorted order of keys or values. Though, if you want to process keys, values or entries of an HashMap in sorted order, you can get the data from the HashMap and then potentially use a TreeMap (when you want to sort a HashMap by key) or LinkedHashMap (when you want to sort a HashMap by value) to store entries in sorted order. This is also the way, we used to sort HashMap before Java 8. 

3 ways to Find First Non Repeated Character in a String - Java Programming Problem Example

Write a Java program to find the first non-repeated character in a String is a common question on coding tests. Since String is a popular topic in various programming interviews, It's better to prepare well with some well-known questions like reversing String using recursion, or checking if a String is a palindrome or not. This question is also in the same league. Before jumping into the solution, let's first understand this question. You need to write a function, which will accept a String and return first non-repeated character, for example in the world "hello", except 'l' all are non-repeated, but 'h' is the first non-repeated character.

Can you take Spring Professional Certification without Training Course? [Yes]

Hello guys, I have a big news to share with you now. Since 5th April 2024, you can take Spring certification without any mandatory training or Spring Pro content. So after a flip flop of making training mandatory, Spring certification is free again. Vmware, the company behind Spring, after acquiring Pivotal has reversed the earlier decision announced on 10th May 2017 by Pivotal, the previous owner of Spring Framework, that "Spring Certification Exams are now available for individual purchase, without enrolling in the course". This was one of the most discouraging changes in the Spring certification program since it's launched 10 years back. The cost of Spring certification was the single, biggest obstacle for many experienced Java and Spring developers to get certified for their Spring framework skills.

Top 25 Apache Kafka Interview Questions Answers for Java Developers

Hello, guys if you are preparing for the Java Developer or Apache Kafka interview and looking for frequently asked Apache Kafka interview questions and answers then you have come to the right place. Earlier, I have shared the best Kafka courses and popular interview questions on Java, JMS, Spring Boot, and Hibernate and in this article, I Am going to share 20 frequently asked Apache Kafka interview questions with answers. Over the years, Kafka which is developed by Apache Software Foundation has gained popularity because of its immense capability of data processing and become a standard tool for high-speed and reliable messaging. 

Review - Is Grokking the System Design interview Course on DesignGuru Worth it?

Hello guys,  we are here again today for another exciting topic to discuss. But today, we will not discuss something related to Java or any other language or spring boot. Today, we will discuss something that is immensely practical and has the potential to land you very high-paying jobs. Today we are going to review a course that focuses on System Design! System Design is crucial for coding interviews! And it's also one of the most challenging topics to master. I have shared the best System design courses for coding interviews and books in the past. Today, I will review one of the top system design courses for technical discussions, Grokking the System Design Interview by Design Gurus.

Top 30 Programming questions asked in Interview - Java C C++ Answers

Programming questions are an integral part of any Java or C++ programmer or software analyst interview. No matter which language you have the expertise it’s expected that you are familiar with the fundamentals of programming and can solve problems without taking the help of API. Programming questions like reversing String using recursion or how to find if Array contains duplicates are some popular examples of programming question in Java. Programming questions present a lot of challenges Especially to Java developers as compared to C++ programmer and I think, One reason for this is powerful Java API; Which has a method for almost every need and you rarely need to write by your own or there are lots of third-party library from Apache, Spring, Google and other open sources.

Review - Is ByteByteGo System Design Interview Course by Alex Xu Really Worth it in 2024?

Hello guys, if you are preparing for System Design Interview in 2024 then you may have most likely come across names like ByteByteGo, Alex Xu or System Design Interview - An Insider Guide by Alex Xu, and if you are wondering what they are or you know about them but thinking whether ByteByteGo is worth it or not? then you have come to the right place. Yes, ByteByteGo is indeed worth considering for your System Design Interview preparation. because its created by Alex Xu, an expert with FAANG interview experience, the platform offers in-depth coverage of system design topics. The author's use of diagrams to explain concepts in detail enhances the learning experience. 

12 Intermediate Database Administrator and Developer Interview Questions on Indexing

A good understanding of Index is very important for any programmer working with database and SQL. It doesn't matter whether you are working as DBA or Application developer, working in Oracle, MySQL, or Microsoft SQL Server or any other database, you must have good understanding of how index works in general. You should know different types of index and their pros and cons, how your database or Query engine chooses indexes and the impact of table scan, index scan, and index seek. You should also be able to build upon your knowledge to optimize your SQL queries as well as troubleshoot a production issue involving long running queries or poor performing queries. This is also a great skill for experience developers with 5 to 6 years of experience under his belt. 

How to Manage Distributed Transaction in Microservices? SAGA and 2 Phase Commit Example Tutorial

Hello guys, managing transaction in a distributed system like Microservices is very challenging and if you don't have a proper approach then you may face production issues and end of with data lose, data corruption and app failure. That's why managing distributed transaction is also an important topic on Microservice interviews. If you are working in Microservices architecture then you may have already heard about the SAGA and 2 Phase Commit etc. and there is also a chance that you may have been asked about those on Java developer interviews. If not, don't worry, in this article, I will tell you about those Microservices design patterns while showing how to manage distributed transactions in Microservices architectures in Java.  

Top 10 Websites to Learn System Design and Software Design in 2024 - Best of Lot

Hello guys, if you are preparing for System design Interview and looking for best resources to master Software design and System design then you have come to the right place. Earlier, I have shred best System Courses, Books, System Design Interview Guide, Cheat Sheets, and System Interview Questions and in this article, I am going to share best places to learn System design in 2024. Before we get to the best websites that will teach you everything you need to know about system design, let me tell you a little bit about what it really is. Systems design is basically the process of defining elements of a system including modules, architecture, components, interface, and data for a system based on a specific set of requirements. It can also refer to the process of defining, developing, and designing systems. These designs have to satisfy the specific needs of a company or an organization.

Top 10 Courses to Learn JavaScript in 2024 - Best of Lot

There is no doubt that JavaScript is the most popular programming language at this moment, and it's also confirmed by StackOverFlow's Survey. You can build static websites, web applications, native mobile applications (yes, you can do that too), desktop applications, and even server-side applications in JavaScript. It also makes you a hundred times more employer as there are tons of web development jobs out there. Because of that, more and more developers are learning JavaScript to become web developers.

Top 10 System Design and Software Analysis and Design Books in 2024 - Best of Lot

Hello guys, System design and Software design are two important topic for coding interviews and also two important skill for Software developers. Without knowing how to design System you cannot create new software and it will also be difficult to learn and understand existing software and system. That's why big technical companies like FAANG pays special attention to System design skill and test candidates thoroughly. If you want to learn System design and looking for best resources like best System design books and courses then you have come to the right place. Earlier, I have shared best System design online courses, as well as Software architecture courses,  and common System design questions and in this article, I am going to share with you best System design books to learn Software design. 

Top 10 Websites and Online Platforms to Learn Git for FREE in 2024 - Best of Lot

Hello guys, like many programmers, I have also worked with a lot of source control systems like SVN, CVS, TFS, VSS, Mercury, and I had always wondered why so many source control systems? Why not just one. It's one of the necessary software tools for development, and everyone needs a version control and code repository, there should be a standard solution. It seems Git and Github have solved that problem now. Now, Git is everywhere from open source to closed source, from small startups to big Investment banks, but there were still legacy projects which were lying on SVN and CVS, but they are now also started moving towards it.

Top 8 Online Courses to Learn Docker and Kubernetes in 2024 - Best of Lot [UPDATED]

Hello guys, how are you doing? Are you on track to accomplish your goals this year? I am sure you had made goals when this year was started, but if not, you can still check out 10 Things Java developers can learn in 2024. It's never too late. From my experience with interacting with many software developers, it seems DevOps, Docker, Kubernetes and Cloud Computing is the top priority for many programmers this year, especially senior Java developers. I have been receiving a lot of queries, emails, and chats about how to learn Docker and Kubernetes, two of the most popular DevOps tools. When it comes to learning, nothing beats personal training, but that's not always feasible; hence we need to rely on self-learning using books and online courses, and that's what I will suggest to you in this article.

How to Crack Java Programming Interviews in 2024? Topics, Courses, Books, and Questions

Java Interviews are a little bit different than traditional programming interviews on tech giants and product-based companies like Google, Amazon, Microsoft, or Facebook. First, even though it has questions from Data Structures and Algorithms like String or Array, you can still manage to clear Java interviews if you are not an expert on them. The questions are a little bit easier and more practical than those companies. Another essential thing about Java interviews are questions based upon Java programming language and JDK API. Since Java is also an Object-oriented programming language, you will find lots of OOP questions there.

Top 10 System Design Courses for Beginners and Experienced Developers in 2024 - Best of Lot

Hello guys, if you are preparing for System design interview and looking for best online courses to learn essential System design concepts like load balancing, API Gateway, scalability, Microservices architecture as well as learn how to solve popular System design questions like how to design YouTube, WhatsApp, Parking Lot, Library System as well when to use NoSQL and SQL then you have come to the right place.  In the past, I have shared best System Design Books, Free System design courses,  System design prep guide, and System Interview Questions and in this article, I am going to share best System Design Courses for beginners and experienced Software Engineer to level up their System Design skills in 2024. 

100+ System Design Interview Questions and Problems for Software Engineers

Hello guys, if you are preparing for System Design interviews then you may know that you have to prepare for theory questions as well as System design problems where you need to design a real world system like WhatsApp, YouTube or DropBox. Theory questions are mostly based upon System design basics and core concepts like Scalability, Caching, database sharding, load balancer, API gateway, security, proxies, messaging queues and software architecture, particularly Microservices. I have been sharing a lot of system design preparation material from last few years, in for example, in the past, I have shared System Design Interview Prep Guide as well as best System design interview books, courses, cheat sheets, and websites and in this article, I am target to share 100+ System Design Interview questions as well as System Design Problems.

Top 6 Free Data Structure and Algorithm Courses for Java and C Programmers

Data Structure and Algorithm is one of the essential topics for programmers, both to get a job and do well on Job. Good knowledge of data structure and algorithm is the foundation of writing good code. If you are familiar with essential data structures like an array, string, linked list, tree, map, and advanced data structure like Tries, AVL trees, etc and know when to use which data structure and compute the CPU and memory cost of your code in terms  Even though you don't need to write your own array, linked list or hash table, given every major programming SKD provides them like JDK or C++ STL library, you will need to understand them so that you can use them in right place. 

Using the right data structure can drastically improve the performance of an algorithm.

Design a Vending Machine in Java - Interview Question

How do you design a Vending Machine in Java? is one of the popular Java interview questions mostly asked at Senior level Java developer Interviews. In a typical coding interview, you will be given a problem statement to develop a vending machine and within a limited time, usually, 2 to 3 hours you need to produce a design document, working code, and unit test in Java. One of the key advantages of such Java interviews is that you can test many essential skills or a candidate in one go. In order to complete the design, coding, and unit testing of a Vending machine, a candidate needs to be really good in all three departments. Recently, I have also seen this question on System Design Interviews, where interviewer want to check experienced developers knowledge on various Software architecture components and design decision. 

Top 7 Spring Microservices Courses with Spring Boot and Spring Cloud in 2024 - Best of Lot

Microservices is the new buzzword in software development word and everybody is talking about it, but it's been in practice for quite some time especially in the form of RESTful web services. The idea of Microservices is simple, breaking a big monolithic application that contains everything from UI to service layer to database into small chunks of applications that are loosely coupled and can work on their own. For example, in a company like Uber, you could have several applications providing different services e.g. discovering when a driver is online or a passenger is searching for a cab, finding a route, traffic, and handling payments. These small applications are known as Microservices.

Top 10 Microservices Design Patterns and Principles - Examples

Hello guys, if you are using Microservice architecture and want to learn about different Microservice design patterns and principles to better architect your application then you have come to the right place. Earlier, I have shared the best Java Microservices courses and books for Java developers, and in this article, I am going to share the essential Microservice design principle and patterns. We will cover patterns like Event Sourcing, Circuit Breaker, SAGA, CQRS, Strangler, Database per Microservices, Backend for Frontend (BFF), Service Discovery,  and API Gateway and principles like Scalability, Flexibility, Resiliency, etc. When you developing an enterprise application, it is good to move with micro-services rather than move with a monolithic architecture. 

Top 5 Java Design Pattern Courses for Experienced Java Developers in 2024 - Best of Lot

Hello guys, today, we'll talk about design patterns and some of the best online courses to learn design patterns in Java from scratch. If you are wondering what is a design pattern and why Java developers should learn them? then let me give you a brief overview. Design patterns are nothing but a tried and tested solutions of common programming problems, for example, the creational design patterns deal with the problems of object creation. They exist from a long time but made popular by famous Gang of four of Erich Gamma, John Vlissides, Ralph Johnson and Richard Helm in their classic 1994 book Design Patterns: Elements of Reusable Object-Oriented Software, also known as GOF design patterns. This book documented 24 design patterns which are reusable to solve common programming problems. 

Top 10 Courses to Learn Spring Framework in Depth in 2024 - Best of Lot

Spring Framework is an essential skill for Java developers, not only to get a job as a Java developer but also for your career advancement. Since Spring is now used in almost every Java project, it becomes virtually mandatory to learn the Spring framework. Now, the question comes, what is the best way to learn the Spring framework? Are there any online courses out there that are focused on Spring? What are some good books and resources for learning Spring? These questions are widespread among Java developers, and I often see them on forums, online chat channels, and even many of my readers also ask this to me on Facebook chats and email. Well, the best way to learn any technology is by coaching, online courses, and books.

Difference between @Autowired and @Inject annotation in Spring?

What is the difference between @Autowired and @Inject annotation in Spring is one of the frequently asked Spring questions on Java interviews? Since everybody is now moved or moving to annotation-driven and Java configuration in Spring, this question has become even more important for prospective candidates looking for a Java web development job using the Spring framework. The @Autowired annotation is used for auto-wiring in the Spring framework. If you don't know, autowiring is a process on which the Spring framework figure out the dependencies of a Spring bean, instead of you, a developer, explicitly specifying them in the application context file. You can annotate fields and constructor using @Autowired to tell Spring framework to find dependencies for you.

Top 9 Courses to Learn SQL and Database in 2024 - Best of Lot

Hello guys, if you are a computer science graduate or new to the programming world, interested in learning SQL, and looking for some excellent resources, like books, courses, and tutorials to start with, then you have come to the right place. In the past, I have shared some of the best SQL books and tutorials, and today I am going to share some of the best SQL and database courses to learn and master this useful technology. If you don't know what SQL is and why you should learn it, let me give you a brief overview of SQL for everyone's benefit. SQL is a programming language to work with a database. You can use SQL to create database objects, like tables, stored procedures, etc., and also to store and retrieve data from the database.

Top 8 Udemy Courses to Learn System Design and Software Architecture in 2024 - Best of Lot

Hello guys, if you want to learn Software Architecture and System design in 2024 and looking for best resources then you will be happy to know that  I am going to share  8 best Udemy courses to learn Software architecture and System design for 2024. if you are preparing for technical interviews for Software Engineering job then you may be aware of  Software Design or System design. It is one of the most important but at the same time very tough topic to master and many programmers even experienced developer struggle to solve System design problems during interview, particularly while interviewing with top tech companies like Google, Meta, Amazon, Apple, Microsoft, Netflix etc, popularly known as FAANG (now MAANG) since Facebook is now Meta. 

Top 5 Courses to Learn Hibernate and JPA in 2024 - Best of Lot

Hibernate is one of the essential frameworks for Java and Java EE or JEE programmers, especially if you are working on the server-side of a Java Web development project. It's an ORM tool or a framework that allows you to deal with only objects while Hibernate takes care of your data on your behalf. For example, instead of writing classes with SQL to load, save, and update data using the DAO design pattern, you can simply use the Hibernate framework in your project. It will allow you to deal with just objects while it will load, save, and update data in the background. It's also one of the top Java frameworks in my list of top 10 Java frameworks Programmers can learn.

Top 20 Spring and REST Interview Questions Answers for Java/JEE Programmers

Hello guys, I have been sharing a lot of REST with Spring tutorials from last a couple of weeks and today, I am going to share some of the frequently asked Spring and REST interview questions to Java developers applying for Web developer roles. Since Spring Framework is the most popular and the standard framework for developing Java web application and RESTful Web Services, a solid knowledge of Spring core and Spring MVC is expected from any senior Java developer, but if the job description mention about REST and Web Services, you also need to be aware of how to develop RESTful Web Services using Spring Framework?.

Top 5 Books to Learn Spring framework and Spring MVC for Java Programmers

Spring and Spring MVC is one of the most popular Java frameworks, and most of the new Java projects use Spring these days. Java programmer often asks questions like which books are good to learn Spring MVC or the best book to learn Spring framework etc. If you are looking for the best Spring Framework books, then you have come to the right place. Earlier, I shared the best Spring Framework courses and best Spring Boot courses, and in this article, I will share the best books to learn Spring Framework for Java developers. There are many books to learn Spring and Spring MVC, but only certain books can be considered good because of their content, examples, or how they explained the concept involved in the Spring framework. 

How to POST JSON request from Linux to test RESTful Web Services? Example

Even though, Postman is a great tool and chrome plugin to test RESTful Web services for Java developers, I often find myself using "curl" or "cURL" command in Linux for testing RESTful Web Services, particularly Java web services built using Spring or Spring Boot framework. The curl command is easily available on most of Linux hosts and you just need to type a command to sent various types of HTTP requests to your application from Linux command line, as shown here. Though, many RESTful web developer and tester knows this trick, they mainly use GET request to access data from web service and  many of them struggle to send HTTP POST request containing JSON data to create new resources. 

Role based Access control using Spring Security and MVC, Mapping LDAP Groups to Authorities for Authorization

Authentication and Authorization is an integral part of any Java enterprise or web application. Since most of the company uses LDAP Active directory for authentication, authorization, and Role-based access control (RBAC), it's good to know How to implement Role-based access control using Spring MVC and Spring Security. This is the second part of my articles on using Spring Security for authentication and authorization in Spring MVC based Java application. In the last part, we have learned about doing LDAP authentication against Windows active directory, and in this Spring Security tutorial, we will learn How to map LDAP groups to authorities for implementing Role-based access control or authorization.

3 ways to solve java.lang.NoClassDefFoundError in Java J2EE

I know how frustrating is to see "Exception in thread "main" java.lang.NoClassDefFoundError" while running your Java application. This is one of the dreaded problem in Java  which is also a manifestation of NoClassDefFoundError in Java. I have seen it a couple of times and spent quite a lot of time initially to figure out what is wrong, which class is missing etc. The first mistake I did was mingling java.lang.ClassNotfoundException and NoClassDefFoundError, in reality, are totally different, and my second mistake was using the trial and error method to solve this java.lang.NoClassDefFoundError instead of understanding why NoClassDefFoundError is coming, what is the real reason behind NoClassDefFoundError and how to resolve this.

10 Examples of JdbcTemplate in Spring Framework

Hello Java programmers, If you have been using the Spring framework then you may know that the JdbcTempalte is one of the most useful classes of the Spring framework. The JdbcTempalte class provides lots of convenient methods for performing database-related tasks that take the pain away from using the JDBC API. If you have worked in any real-life Java project which connects to a Database using JDBC then you know that JDBC API is not very convenient to use as it requires a lot of boilerplate code. For example, to execute a simple SELECT query, you first need to create a Connection and Statement object to execute the query and iterate through a ResultSet Object to get the result of the query. Finally, you need to close all of these resources to prevent resource leaks in Java.

How to Solve java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener in Spring? [Example]

If you have worked in Spring MVC then you may be familiar with  
java.lang.ClassNotFoundException: org.springframework.web.context.ContextLoaderListener, 
which is common problem during deployment. Spring MVC throws  java.lang.ClassNotFoundException:                           org.springframework.web.context.ContextLoaderListener ,
when its not able to find org.springframework.web.context.ContextLoaderListener class which is used to load spring MVC configuration files like application-context.xml and other Spring Framework configuration files defined in context-param element of web.xml in an Spring MVC web application as:

How to Consume JSON from RESTful Web Service and Convert to Java Object - Spring RestTemplate Example

So far, I have not written much about REST and RESTful web service, barring some interview questions like REST vs. SOAP, which is thankfully very much appreciated by my readers, and some general suggestions about the best books to learn REST and best REST courses in the past. Today I am going to write something about how to consume JSON from a RESTful Web Service in Java using Spring Framework? I will also talk about how to convert the JSON to Java objects using Jackson. You will also learn about the RESTTemplate class from the Spring MVC framework, and how you can use it to create a REST client in Java in just a few lines of code.

Spring Boot + Kafka Example (Single and Multiple Consumer) in Java

Hello guys, if you want to use Apache Kafka with Spring Framework or Spring Boot and looking for an example then you have come to the right place. In the past, I have shared the best Spring Boot courses as well as best Apache Kafka courses for Java developers, and in this article, I am going to share how to use Apache Kafka with Spring Boot. You will learn both, to publish and consume messages from Apache Kafka topics in your Spring boot application. By the way, if you don't know, Apache Kafka is an open-source stream-processing software platform developed by LinkedIn and later they donated to Apache software foundation, king of open source development in Java world. 

How to set an "Accept:" header on Spring RestTemplate request? Example Tutorial

Hello Java programmers, if you have been using Spring for REST API development, both creation and consumption then you know that RestTemplate is one of the most commonly used tools for REST service invocations. So one of the major problems you might have in this RestTemplate is that how to set an "Accept" header on Spring RestTemplate request.  In the last article, I have shown you how to POST and Consume JSON using RestTemplate in a Spring Based Java application and In this tutorial, we will go through some important points on how to add headers to RestTemplate and fix the errors related to them. 

Top 133 Java Interview Questions Answers for 2 to 5 Years Experienced Programmers

Time is changing and so is Java interviews. Gone are the days, when knowing the difference between String and StringBuffer can help you to go through the second round of interview, questions are becoming more advanced and interviewers are asking more deep questions. When I started my career, questions like Vector vs Array and HashMap vs Hashtable were the most popular ones and just memorizing them gives you a good chance to do well in interviews, but not anymore. Nowadays, you will get questions from the areas where not many Java programmer looks e.g. NIO, patterns, sophisticated unit testing or those which are hard to master e.g. concurrency, algorithms, data structures and coding.

Top 22 Spring Interview Questions Answers for Java Programmers [UPDATED]

Hey Java Programmers, if you are preparing for a Java developer interview then you should pay special attention to Spring framework-related questions. Spring framework interview questions are on the rise on Java web development and core Java interviews.  This is obvious given Spring Framework is the best most popular framework available for Java application development and now Spring IOC container and Spring MVC framework are used as a de-facto framework for all new Java development. Because of its popularity,  interview questions from the spring framework are top on any list of Java Interview questions and you should also prepare different Spring topics like Spring Boot, Spring Data JPA, Spring Security, Testing and Spring Cloud, etc to do well on Java developer interviews. 

How to fix @Autowired - No qualifying bean of type found for dependency in Spring Boot? [Solved]

Hello guys, if you are working in a Java and Spring Boot project and you are getting errors like "@Autowired - No qualifying bean of the type found for dependency " then you have come to the right place. Earlier, I have shared how to solve error creating bean with name in Spring framework and In this tutorial, we are going to discuss how to fix @Autowired - No qualifying bean of the type found for dependency. When we come across the org.springframework.beans.factory, we need to be careful. Whether there isn't a qualifying bean of type XXXX accessible, we should see if there is a spring bean called XXXX in the runtime. In most cases, we simply try to inject a bean that isn't defined.

Is "Java Concurrency in Practice" still Valid in the Era of Java 21?

Hello guys, one of my reader Shobhit asked this question on my blog post about 12 must-reads advanced Java books for intermediate programmers - part 1. I really like the question and thought that many Java programmers might have the same doubt whenever someone recommends them to read Java Concurrency in Practice. When this book came first in 2006, Java world was still not sure of about new concurrency changes made in Java 1.5, I think the first big attempt to improve Java's built-in support for multi-threading and concurrency. Many Java programmers were even not aware of new tools introduced in the API like CountDownLatch, CyclicBarrier, ConcurrentHashMap, and much more. The book offered them the seamless introduction of those tools and how they can use them to write high-performance concurrent Java applications.

Difference between @Component, @Service, @Controller, and @Repository in Spring

Before you learn the difference between @Component, @Service, @Controller, and @Repository annotations in the Spring framework, it's important to understand the role of @Component annotation in Spring. During the initial release of Spring, all beans are used to be declared in an XML file. For a large project, this quickly becomes a massive task, and Spring guys recognize the problem rather quickly. In later versions, they provide annotation-based dependency injection and Java-based configuration. From Spring 2.5 annotation-based dependency injection was introduced, which automatically scans and registers classes as Spring bean which is annotated using @Component annotation.

Top 20 Spring Framework Annotations Java Developers Should Know

Hello guys, annotations are quite important when working in modern Java application as almost all frameworks and libraries nowadays use annotations, including Spring Framework. There was time when we need to remember classes and methods to make effective use of JDK or any open source library but now we also need to remember annotations. For example, to use JUnit you must know about annotations like @Test, @BeforeEach, @AfterEach, @Disabled and so on. Similarly for Spring framework you need to know annotations like @Configuration, @Bean, @Component, @Service, @Value, @Autowired, @Repository, @Qualifier, @Required and more. 

Top 10 Java and Web Development Courses from Udemy in 2024 - Best of Lot

Hello guys, I am sure you all have made your goals and resolutions for this year, like what to learn in 2024. If you haven't, then check out my post 10 Things Java programmers should learn in 2024 for some ideas. If you have already made your goal, then it is time to think about how you are going to achieve them. For example, my top 5 goals in 2024 are to learn Java 17, AWS, Microservices, Spring 5, and Spring Security 5, but how am I going to learn them? Well, I like books and online courses, and that's why I have been searching for some excellent courses on Java, Spring Boot, Microservices, Docker, Web development, and Spring. 

Top 17 Spring AOP (Aspect-Oriented Programming) Interview Questions Answers

If you are preparing for Java and Spring Developer interviews or Spring professional certification then a good knowledge of Aspect-oriented Programming or AOP is required. It's a boring and tough topic but important from a Spring interview and Spring certification point of view and that's where these 15+ AOP interview questions come really handy. You can use them to revise key AOP concepts before any telephonic or face-to-face interview as well as to learn and explore more about Aspect-Oriented Programming. In this article, I am going to share frequently asked AOP interview questions and also tried to answer AOP questions give on the official Spring certification exam guide.

20 Design Patterns and Software Design Interview Questions for Programmers

Design patterns and software design questions are an essential part of any programming interview, no matter whether you are going for a Java interview or a C#  interview. In fact, programming and design skills complement each other quite well, people who are good programmers are often good designers as well as they know how to break a problem in to piece of code or software design but these skills just don’t come. You need to keep designing, programming both small-scale and large-scale systems, and keep learning from mistakes. 

Top 5 Spring Boot Features for Java Development

You might have heard about Spring Boot and its magical powers about creating a Spring Web application in just under 140 characters which can be written in a tweet, but what does that really mean? What are those features which provide Spring Boot such power and make Spring application development so easy? Well, that's what you will learn in this article, but if you are in hurry let me tell you that you will learn about Spring Boot's auto-configuration, Starter dependencies, Spring Boot CLI, Actuator, and Spring Initializer feature in detail. These are the feature that takes away most of the pain and friction associated with writing a Spring-based Java web application.

What is bean scope in Spring Framework? Example Tutorial

Java classes or POJO which are managed by Spring Framework are called Bean or Spring Beans and Bean scope in Spring framework or Spring MVC is scope for a bean managed by Spring IOC container. Bean scope refers to the lifecycle and visibility of a bean instance in spring container. The scope determines how long the bean instance will live and how it will be shared with the other parts of application. You may know that Spring is a framework that is based on Dependency Injection and Inversion of Control and provides bean management facilities to Java application. In Spring-managed environment bean (Java Classes) are created and wired by the Spring framework. Spring allows you to define how those beans will be created and the scope of the bean is one of those details. Scope are similar to access modifiers in Java which specifies visibility of a particular class. 

Difference between @RequestMapping and @GetMapping in Spring MVC? Example

Hello Java programmers, if you are wondering what is the difference between @RequestMapping and @GetMapping annotation in Spring MVC and when and how to use them then you have come to the right place. Earlier, I have shared the best Spring MVC courses and books, and In this tutorial, we are going to discuss about Spring MVC and spring boot web services. In there, most of the interviewers asked about the difference between @RequestMapping and @GetMapping annotations in spring applications. Before going to discuss the difference between these annotations, first, understand what is @RequestMapping?, How do we use the @RequestMapping?, What is a request? and types of them.

Spring Boot @Transactional Annotation Example - How to Manage Transactions using Spring Framework?

One of the most essential parts of Spring MVC is the @Transactional annotation, which provides support for transaction management and allows developers to concentrate on coding business logic rather than worrying about data integrity in the event of system failures. In other words, @Transactional annotation  simplifies the process of transaction management and it allows you to specify transactional behavior directly within your code, typically at the service layer. You can put @Transactional annotation both at the class level and method level. When you put the @Transacational at the class level, it applies to all the public method of the class but when you put the @Transacational annotation at the method level. It only applies to that method. 

4 Ways to take Heap dump in Tomcat and Java and 3 Tools to Analyse .hprof files

The heap dump is a great source of information on identifying memory related issues on Java application e.g. web and application servers like Tomcat, WebLogic, JBoss, WebSphere and IDEs like IntelliJIDEA and Eclipse. When you take heap dump all live objects of heap with their count and other details are written into a huge file (the .hprof file) for analysis. The name and location of heap dump file is provided by command you use to take the heap dump. There are many command line tools in JDK e.g. jmap and jcmd which can be used to take the heap dump in Java.