How to Print all leaf Nodes of a Binary tree in Java [ Coding Interview Questions]

This is another interesting coding problem that is based on a binary tree and mostly asked beginner programmers. If you have some experience in solving binary tree-based problems then it's rather easy to solve because, like many other binary tree algorithms, you can use recursion to print all leaf nodes of a binary tree in Java. Since the tree is a recursive data structure, you can apply the same algorithm to both the left and right subtree. In order to solve this problem, the first thing you should know is what is a leaf node because if you don't know that then you won't be able to solve the problem. Well, a leaf node is the one whose left and right child nodes are null.

10 Examples of Array Data Structure in Java

Without any doubt, the array is one of the most used data structures in all programming languages, including Java. Pick up any programming language be it functional, object-oriented, imperative, or even scripting languages like Python, Bash, and Perl, you will always find an array. That's why it's important for any programmer to have a good understanding of the array data structure. Like any other data structure, the array also provides a way to organize and store objects, but the way it does makes all the difference. An array is used to store elements in the contiguous memory location and many C, C++ programmers can take advantage of a pointer to work with an array.

Top 40 Binary Tree Coding Interview Questions for Programmers

Hello guys, if you are preparing for coding interviews and want to master tree-based questions then you have come to the right place. A tree is one of the most important data structures because it allows you to store hierarchical data as opposed to an array and linked list which allows storing linear data. That's why knowledge of tree data structure is very important from an interview point of view. A lot of programmers and my readers have been asking me to share some binary tree-based coding interview questions, just like I have done for the array, linked list, string, software design, patterns, hash table, and data structure in general. 

Top 25 Linked List Coding Interview Questions for Java Programmers

Hello guys, if you are preparing for Software Development interview or want to become a Software Engineer then you must pay full attention to two important topics: first is Data Structure and Algorithms, and second is System Design. These two topics are very essential and you will always find questions from these in any coding interview. They are also the most difficult to crack as they are very vast, no matter how much you will prepare there will be certain questions which you don't know but if you have solid knowledge of fundamental data structure like array, linked list, binary tree, hash table, heap, and graphs as well sorting and searching algorithms like quicksort, merge sort, selection sort, insertion sort, binary tree as well advanced String and graph algorithms then you can still do well.

[Solved] How to check if two String are Anagram in Java? Example

Hello guys, if you are preparing for Coding interviews then you already know that String is one of the most popular topics. You will be bound to get some string-based coding problems on interviews. If not, you have come to the right place becuase we'll look at one of the most popular String programming interview questions today,  how to check if two given strings are Anagram of each other? Two String is said to be an anagram of each other, if they contain exactly the same characters but in a different order. For example "ARMY" and "MARY" are an anagram of each other because they contain the exact same characters 'A', 'R', 'M' and  'Y'.

How to create a String or int Array in Java? Example Tutorial

There are several ways to create an array in Java, for example, you can declare the array without initializing it, or you can create and initialize the array in the same line. If you want to make an array with values, then you need to first decide which type of array you want to create? e.g., do you want a String array, which can contain String objects like "abc," "def," or do you want to create an int array that contains int values like 10, 20, etc. In Java, you can create an array of any type, including primitives like byte, int, long, and objects like String, Integer, and other user-defined objects. Let's some code to make a new array in Java.

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.

How to check If two Strings Array are equal in Java? Example Tutorial

Hello guys, if you are wondering how to check if two given String array are equal, I mean they contain same number of elements with same values and looking for solution then you have come to the right place. In the past, I have shared several coding questions on different data structures like linked list, binary tree, string, and even system design and today, we shall be working with arrays, Oh arrays are so pretty! And it’s very simple to learn. Having understood the concept of arrays the goal is to be able to check if two String arrays are equivalent. 

Top 5 Free Servlet, JSP, Java FX, and JDBC Courses for Java Web Developers in 2025 - Best of Lot

If you are a Java developer working on a Java JEE projects like a Java Web application running on Tomcat or Glassfish, or you want to get into that by learning server-side technologies like Servlet, JSP, and JDBC, then you have come to the right place. In this article, I will share some free online courses to learn Servlet, JSP, and JDBC at your own pace. If you want to become a rockstar Java web developer, then you must have a good understanding of these essential web technologies before you learn frameworks like Spring and Hibernate. These frameworks work on top of these basic technologies, and if you don't know them, then you would often struggle to debug and troubleshoot problems in the real world.

Top 6 Dynamic Programming Online Courses for Coding Interviews in 2025 - Best of Lot

Hello guys, if you are preparing for a coding interview but struggling to solve Dynamic programing based coding problems and looking for the best resource to improve your Dynamic programming skill then you have come to the right place. Earlier, I have shared the best coding interview courses and best Recursion courses,  as well as popular  Dynamic programming problems from interviews, and today I am going to share the best online courses to learn Dynamic programming in depth.  Dynamic programming simply means that plain recursion can be optimized when there are repeated calls for some inputs.

5 Free Online Courses to Learn Kotlin in 2025 - Best of Lot

Hello guys, If you are in Android application development or server-side Java development, then you might have heard about the Kotlin programming language, created by JetBrains, the company behind popular IDEs like IntelliJIDEA, PyCharm, and WebStorm. Kotlin is also Google's official language for developing Android apps. If you don't know what Kotlin is and why you should learn Kotlin, then let me tell you that Kotlin is a mature programming language that offers many benefits over traditional programming languages like Java which has been time-tested over the last 25 years. Kotlin is designed to solve pain points of Java programming language like verbose nature and boilerplate.

Top 6 Free Courses to Learn Bootstrap Online for Beginners in 2025 - Best of Lot

Bootstrap is one of the most popular front-end libraries, which provides a customizable HTML, CSS, and JavaScript template for creating a modern and responsive website. All the beautiful websites you see these days with large fonts and slick form fields are built using Bootstrap. If you want to learn Bootstrap and looking for some excellent online courses, then you have come to the right place. In the past, I have shared advanced CSS courses to learn Flexbox, Grid, and SaaS, and in this article, I will share some of the excellent Bootstrap courses, which are also free, and you can use them to kick-start your journey with the Bootstrap framework. If you are interested in modern web development, this is the framework you must learn this year.

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. 

[Solved] How to Find Repeated Characters in a given String with count in Java? Example

This is another interesting coding problem or programming exercise for beginner programmers. How do you find repeated or duplicate characters in a given String and their count? You can solve this coding problem in any programming language of your choice like Java, Python, Ruby, or even JavaScript. I'll explain the logic and solution which is easy to implement in the above programming languages and I'll provide code in Java, which is my favorite programming language.  In order to solve this problem, You need to first check if a String contains any duplicate characters or not, and then if it contains any duplicate letters then find out how many times they appear in the given input String.

How to solve Two Sum Array Problem in Java? Example

Hello guys, if you have been solving data structure and algorithms problems or been through a couple of coding interviews then you might be familiar with the classical "Two Sum" problem. It's one of the classical coding problems of finding two numbers in a given array whose sum is equal to a given target number. It's a good problem to learn how array data structure works and programming basics like loops, conditionals, and operators. It's also good for developing your problem-solving skills and coding sense, which will help you in the long run. This is also a popular Leetcode problem and is commonly asked in coding interviews to both beginners and intermediate programmers.

6 Essential Data Structures Java Programmer should Learn

Hello guys, Data Structure is a building block of programs. It's even said that  "Data Structure + Algorithms= Program". That's why a good knowledge of data structure is very important for any programmers, including Java developers. Data structure gives you the option to store your data so that you can access it based on your requirement. For example, if you want a fast search based upon the username then you can use HashMap, but that's only possible if you know data structure and their implementations in the programming language you are using, and that's what you will learn in this article. 

Post order traversal Algorithms for Binary Tree in Java with example

In the last couple of articles, you have learned about pre-order and in-order tree traversal algorithms in Java, and today, you will learn about the post-order traversal in a binary tree. It is the toughest of all three tree traversal algorithms and programmers generally struggle to implement this when asked in a coding interview. Hence it makes sense to understand and practice this algorithm before going for the interview. The post order traversal is also a depth-first algorithm because you go deep before you visit other nodes on the same level.

How to check if an array includes a value in JavaScript? Example Tutorial

Hello Javascript developers, if you are wondering how to check if an array contains a particular value or not in Javascript then you have come to the right place. In the last article I showed you how to remove empty elements from the JavaScript array and today I will show you 3 ways to check if an array contains a particular value in Javascript. I have been sharing a lot of Javascript resources like the best JavaScript courses, books, websites, and Javascript interview questions, along with many JavaScript and React tutorials, and today, we are going to see an example of the includes() method of the array in JavaScript to find out if an array has a particular value or not.  

How to sort an Array in descending order in Java? Example Tutorial

Sorting an array is one of the common tasks in Programming and you have many algorithms to sort an array, like QuickSort, MergeSort which provides O(NLogN) time performance, and Bucket Sort, Counting Sort, and Radix Sort algorithms which can even sort some array in O(N) time. But, you hardly need to code these algorithms by hand when it comes to writing real code. The Programming language you will use already has tried and tested implementation for those algorithms and that's what you will learn in this article. In Java Programming language, it's easy to sort an array, you just need to call the Arrays.sort() method with a Comparator which can sort the array in the order you want but it highly depends upon which type of object is stored in the array.

QuickSort Algorithm Example in Java using Recursion - Tutorial

The Quicksort algorithm is one of the very popular sorting algorithms in programming, often used to sort a large array of numbers. Though there is numerous algorithm available to sort a list of objects, including integer, string, and floating-point number, quicksort is best for general purpose. It's a divide and conquers algorithm, where we divide the given array with respect to a particular element, known as 'pivot' such that the lower partition of the array is less than the pivot and upper partition elements of the array are higher than the pivot.

How to remove a number from an Integer Array in Java? [Example Tutorial]

Hello guys, In the last article, you have learned how to reverse an array in place in Java, and today I have come back with another array-based coding interview question. It's also one of the frequently asked coding questions, not as popular as the previous one but still has been asked a lot of times on various Programming Job interviews, particularly to beginners. In this problem, you are asked to write a program to remove a given number from the given array. It may seem easy, but the trick is that because an array is a fixed data structure and you cannot change the length of the array once created. 

How Binary Search Algorithm Works? Java Example without Recursion

The binary search algorithm is one of the fundamental Computer Science Algorithms and is used to search an element in a sorted input set. It's much faster than the linear search which scans each and every element and improves performance from O(n) to O(logN) for searching an element in the array. In order to perform the binary search, you need a sorted array, so you can either ask the user to enter the array in sorted order or you should sort the array before performing the binary search. It's also one of the popular algorithms for Programming Job interviews. The interviewer often asks candidates to implement binary search algorithms by hand in their favorite programming languages like Java, C++, Python. or JavaScript.

How to declare and Initialize two dimensional Array in Java with Example

An array of more than one dimension is known as a multi-dimensional array. Two of the most common examples of multi-dimensional arrays are two and three-dimensional arrays, known as 2D and 3D arrays, anything above is rare. I have never seen 4-dimensional arrays, even 3D arrays are not that common. Now the question comes when to use a multi-dimensional array? Any real-life example? Well, 2D arrays are very common on platform games like Super Mario Bros to represent screen or terrain; 2D arrays can also be used to represent structures like a spreadsheet, or to draw board games like Chess, which requires an 8x8 board, Checkers and  Tic-Tac-Toe, which requires 3 rows and 3 columns.

How to compare two Arrays in Java to check if they are equal - [String & Integer Array Example]

Hello guys, one of the common Programming, the day-to-date task is to compare two arrays in Java and see if they are equal to each other or not. Of course, you can't compare a String array to an int array, which means two arrays are said to be equal if they are of the same type, has the same length, contains the same elements, and in the same order. Now, you can write your own method for checking array equality or take advantage of Java's rich Collection API. Similar to what you have seen while printing array values in Java, java.util.Arrays class provides convenient methods for comparing array values.

How to Convert or Print Array to String in Java? Example Tutorial

Array and String are very closely related, not just because String is a character array in most of the programming language but also with popularity - they are two of the most important data structure for programmers. Many times we need to convert an array to String or create an array from String, but unfortunately, there is no direct way of doing this in Java. Though you can convert an array to String by simply calling their toString() method, you will not get any meaningful value.  If you convert an Integer array to a String, you will get something like I@4fee225 due to the default implementation of the toString() method from the java.lang.Object class. Here, I show the type of the array and content after @ is hash code value in hexadecimal.

How to implement PreOrder traversal of Binary Tree in Java - Example Tutorial

The easiest way to implement the preOrder traversal of a binary tree in Java is by using recursion. The recursive solution is hardly 3 to 4 lines of code and exactly mimic the steps, but before that, let's revise some basics about a binary tree and preorder traversal. Unlike array and linked list which have just one way to traverse, I mean linearly, the binary tree has several ways to traverse all nodes because of its hierarchical nature like level order, preorder, postorder, and in order. Tree traversal algorithms are mainly divided into two categories, the depth-first algorithms, and breadth-first algorithms. In depth-first, you go deeper into a tree before visiting the sibling node, for example, you go deep following the left node before you come back and traverse the right node.

How to reverse a singly linked list in Java without recursion? Iterative Solution Example

Hello guys, reverse a linked list is a common coding problem from Programming Job interviews and I am sure you have seen this in your career, if you are not, maybe you are a fresher and you will going to find about this very soon in your next technical interview. In the last article, I have shown you how to use recursion to reverse a linked list, and today, I'll show you how to reverse a singly linked list in Java without recursion. A singly linked list, also known as just linked list is a collection of nodes that can only be traversed in one direction like in the forward direction from head to tail. Each node in the linked list contains two things, data and a pointer to the next node in the list.

How to Reverse an Array in place in Java? Example Solution

It's relatively easy to reverse an array if you have the luxury to use another array, but how would you reverse an array if a temporary buffer is not allowed? This is one of the testing array interview questions, which often proved tricky for Java and other beginner Programmers. But, don't worry, I'll tell you how you can solve this problem without losing your cool. Well, you can also reverse an array in place without using an additional buffer. If you know how to access array elements and how to loop over an array in Java using traditional for loop, you can easily solve this problem without using additional space or in-place as described in many Algorithms books and courses, and on Coding interviews.

5 Differences between an array and linked list in Java

The difference between an array and a linked list is one of the frequently asked data structure and algorithm interview questions and you might have seen it before on your telephonic or face-to-face interview. It is also a very popular question during practical exams in Computer Science degree courses like B.E. and B.Tech. It's very simple and easy to answer but you just can't afford to miss this question in an interview. Both array and linked list are two of the most popular and fundamental data structures in Computer Science and Programming, and Java supports both of them.

How to code Binary Search Algorithm using Recursion in Java? Example

Hello guys, In the last article, we have seen the iterative implementation of binary search in Java, and in this article, you will learn how to implement binary search using recursion. Recursion is an important topic for coding interviews but many programmers struggle to code recursive solutions. I will try to give you some tips to come up with recursive algorithms in this tutorial. In order to implement a recursive solution, you need to break the problem into sub-problems until you reach a base case where you know how to solve the problem like sorting an array with one element. Without a base case, your program will never terminate and it will eventually die by throwing the StackOverFlowError.

Post Order Binary Tree Traversal in Java Without Recursion - Example Tutorial

In the last article, I have shown you how to implement post-order traversal in a binary tree using recursion, and today I am going to teach you about post order traversal without recursion. To be honest, the iterative algorithm of post-order traversal is the toughest among the iterative pre-order and in-order traversal algorithm. The process of post-order traversal remains the same but the algorithm to achieve that effect is different. Since post-order traversal is a depth-first algorithm, you have to go deep before you go wide. I mean, the left subtree is visited first, followed by the right subtree, and finally, the value of a node is printed.

7 Examples to Sort One and Two Dimensional String and Integer Array in Java | Ascending, Descending and Reverse Order

Sorting array is a day-to-day programming task for any software developer.  If you have come from a Computer Science background then you have definitely learned fundamental sorting algorithms like the bubble sort, insertion sort, and quicksort but you don't really need to code those algorithms to sort an array in Java because Java has good support for sorting different types of array. You can use Arrays.sort() method to sort both primitive and object array in Java. But, before using this method, let's learn how the Arrays.sort() method works in Java. This will not only help you to get familiar with the API but also its inner workings.  This method sorts the given array into ascending order, which is the numeric order for primitives and defined by compareTo() or compare() method for objects.

Insertion Sort Algorithm in Java with Example

Insertion sort is another simple sorting algorithm like Bubble Sort. You may not have realized but you must have used Insertion sort in a lot of places in your life. One of the best examples of Insertion sort in the real-world is, how you sort your hand in playing cards. You pick one card from the deck, you assume it's sorted, and then we insert subsequent cards in their proper position. For example, if your first card is Jack, and the next card is Queen then you put the queen after Jack. Now if the next card is King, we put it after the queen, and if we get 9, we put it before jack.

How to Rotate an Array to Left or Right in Java? Solution Example

Hello guys, welcome to another post with another array-based coding problem. In the last article, we've learned about finding missing numbers in the array with duplicates, and today we'll solve the problem of rotating an array by left or right by a given number. For example, suppose an integer array {1, 2, 3} is given and it was asked to rate this array to the left by 3 then the result array will look like {2, 3, 1} because it was rotated twice on left. Similarly, if you are asked to rotate the same array twice by right then you'll get {1, 2, 3}, the same array is back. 

How to Remove an Element from Array in Java with Example

There is no direct way to remove elements from an Array in Java. Though Array in Java objects, it doesn't provide any methods to add(), remove(), or search an element in Array. This is the reason Collection classes like ArrayList and HashSet are very popular. Thanks to Apache Commons Utils, You can use their ArrayUtils class to remove an element from the array more easily than by doing it yourself. One thing to remember is that Arrays are fixed size in Java, once you create an array you can not change their size, which means removing or deleting an item doesn't reduce the size of the array. This is, in fact, the main difference between Array and ArrayList in Java.

How to copy Array in Java? Arrays copyOf and copyOfRange Example

There are multiple ways to copy elements from one array in Java, like you can manually copy elements by using a loop, create a clone of the array, use Arrays.copyOf() method or System.arrayCopy() to start copying elements from one array to another in Java. Even though both allow you to copy elements from source to destination array, the Arrays.copyOf() is much easier to use as it takes the just original array and the length of the new array. But, this means you cannot copy subarray using this method because you are not specifying to and from an index, but don't worry there is another method in the java.util.Arrays class to copy elements from one index to other in Java, the Arrays.copyOfRange() method. Both methods are overloaded to copy different types of arrays.

How to implement linked list data structure in Java using Generics? Example

The linked list is a popular data structure for writing programs and lots of questions from a linked list are asked in various Programming Job interviews. Though Java API or JDK provides a sound implementation of the linked list data structure as java.util.LinkedList, a doubly-linked list, you don't really need to implement a linked list of your own for writing production code, but all these interview questions require you to code a linked list in Java for solving coding problems. If you are not comfortable creating your own a linked list, it would be really difficult to solve questions like reversing a linked list or finding the middle element of a linked list in one pass.

Top 20 Tailwind CSS Interview Questions and Answers

Hello guys, if you are preparing for web designer or web developer interview where Tailwind CSS skills are needed and you are looking for common Tailwind questions to prepare for interview then you have come to the right place. Earlier, I have shared common CSS interview questions and Bootstrap questions, another important CSS framework and in this article, I am going to share 20 frequently asked Tailwind CSS interview questions with answers. These questions covers essential Tailwind concepts and if you have worked with Tailwind or used Tailwind in past then you can easily answer these questions but if you forgot and struggle to answer them then you can also checkout one of these best Tailwind CSS books and courses to learn and revise Tailwind concepts quickly. 

8 Difference between TCP and UDP Protocol in Java? Networking Question

What is the difference between TCP and UDP is a popular networking question from Java interviews? Though TCP or UDP is Java independent concept and very likely to be asked in other programming language interviews as well, many programmers do not really understand them clearly. They sure have heard them because TCP and UDP are two of the most important transport protocol of the internet, but when it comes to listing down the difference between them, they fail to mention key differences in terms of ordering, guaranteed delivery, speed, and usage. 

Top 43 Java IO and File System Interview Questions with Answers for 1 to 3 Years Experienced

Good knowledge of Java IO API is important for any Java developer but many of them barely pay attention to Java IO and NIO API, and that's why they often struggle during Java interviews when a question related to Input-Output operation is asked. In the past, I have shared many Java interview questions on topics like Collections, Concurrency, JVM internals, Garbage Collection, OOP, Design Patterns, and Data structure based coding problems, which received good feedback and helped many Java developer on their Java Interview preparation. Consequently, many of my readers were also asking about Java IO and File-based interview questions and this was one of the pending items on my TODO list for quite some time.

Top 24 Java Date, Time, and Calendar Interview Questions Answers

The Date and Time API is a significant one for day-to-day Java development work, but many interviewers don't ask enough questions on this topic. Most of the questions are based on either Java Collection framework like  HashMap, ConcurrentHashMap, or ArrayList or multi-threading concepts like volatile, synchronized, and atomic variables. This is not good, and many interviewers have realized that a good understanding of date and time API is also important for a good Java developer. That's the main reason for increasing date, time, and calendar-based Java interview questions in recent times, particularly in the last couple of years.

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. 

Top 30 Spring Core, Spring MVC and Spring Security Interview Questions Answers

Spring Interview Question is one of the first things Java programmers should prepare before appearing on any Java or Spring interview. With the immense popularity of Spring frameworks like Spring MVC and Spring Boot in the Java world, the focus on Spring skills on interviews increases daily. For those who don't know, the Spring framework is one of the most famous structures for Java applications, which aims to simplify Java development. It revolutionized the Java development when it initially came with concepts of  Dependency Injection and Inversion of Control, which made writing a testable and maintainable Java application

Top 53 Java Programs for 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 35 Java String Interview Questions with Answers for 2 to 5 Years Experienced Programmers

Hello Java Programmers, if you are preparing for a Java developer interview and want to refresh your knowledge about  String class in Java then you have come to the right place. In the past, I have shared 130+ Core Java Interview Questions and 21 String Coding Problems for Interviews and in this article, I am going to share 35 Java String Questions for Interviews. The  String class and concept is a very important class in Java. There is not a single Java program out there which is not use String objects and that's why it's very important from the interview point of view as well. In this article, I am going to share 35 String-based questions from different Java interviews.

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.

How to add or view SSL certificate in Java keyStore or trustStore? keytool command examples

The keytool command in Java is a tool for managing certificates into keyStore and trustStore which is used to store certificates and requires during the SSL handshake process. By using the keytool command you can do many things but some of the most common operations are viewing certificates stored in the keystore, importing new certificates into the keyStore, delete any certificate from the keystore, etc. For those who are not familiar keyStore, trustStore, and SSL Setup for Java application Here is a brief overview of What is a trustStore and keyStore in Java

Difference between StringBuilder and StringBuffer in Java with Example

If you are in a hurry and heading straight to interview then I won't take much of your time, In a couple of words, the main difference between StringBuffer and StringBuilder is between four parameters, synchronization, speed, thread-safety, and availability. StringBuffer is synchronized and that's why thread-safe, but StringBuilder is not synchronized, not thread-safe and that's why fast. Regarding availability, StringBuffer is available from Java 1.0 while StringBuilder was added in Java 5. 

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 5 Free Udemy Courses to Learn React Native Courses for Beginners in 2025 - Best of Lot

Hello guys, if you are learning React Native to make cross-platform apps and looking for some free courses to learn React Native then you have come to the right place. In the past, I have shared the free courses to learn ReactJS, and the best React Native courses, and today I am going to share the best free online training courses to learn React Native. The list includes both React Native crash courses as well as comprehensive courses to learn React Native in depth. There is a huge demand for cross-platform app frameworks like React Native and Flutter which allows you to create native-looking iOS and Android apps with the same code base.

Top 5 Tableau Desktop Specialist Associate Certification Courses on Udemy in 2025 - Best of Lot

Hello guys, if you are preparing for Tableau Desktop Associate Certification or want to become a Tableau Desktop certified associate and looking for the best online courses to start your preparation, then you have come to the right place. In the past, I have shared the best courses to learn Tableau, and today I will share the best course to crack the Tableau Desktop Certified Associate exam. These are the best online courses from sites like Udemy and Pluralsight and were created by experts and experienced Tableau developers. These will help you cover all exam topics and gain all the necessary skills required to pass this prestigious IT certification

Top 5 Udemy Courses to learn Scrappy with Python in 2025 - Best of Lot

Hello guys, web scraping is one of the useful skills, and you can use it for many different projects. For example, you can use web scraping to find the cheapest flight between the two countries, find the cheapest hotels and holiday packages. Python makes it easy to scrape data from the website and store it. Many built-in tools can do web crawling and scraping, and one of the best tools is Scrapy. This tool is a free and open-source tool written in python for web scraping and crawling purposes, and you can use it to extract data from any website.

Top 5 Online Courses to learn Internet of Things (IoT) for Beginners on Udemy in 2025 - Best of Lot

Hello guys, you might have heard about IoT or the Internet of things, one of many buzzes around the technology world. If you are not sure what does IoT means and why you should learn this skill in 2025 then let me give you a brief overview.  The Internet of Things or IoT is any material or machine that has an internet connection other than a general computer that you are using in your daily life or phones and it must have some computational power and some intelligence to be considered as an IoT device such as the cameras and the intelligent refrigerator. If you are looking to learn about the Internet of Things to create some useful projects then you have come to the right place.

Top 5 Online Courses to Learn MySQL Database in 2025 - Best of Lot

Hello guys, if you want to learn MySQL and SQL in 2025 and looking for the best resources like online courses, tutorials, and books then you have come to the right place. Earlier, I have shared the best SQL courses, books, and SQL interview questions and today, I am going to share the best online courses to learn MySQL in 2025. As you most probably know, MySQL is one of the big players in the Big Data technological ecosystem. It is one of the most popular databases in the world and has wide-ranging capabilities. It is used in a wide variety of industries, and so every half-decent programmer should at least have a basic understanding of MySQL.

Top 6 Blockchain Courses and Certifications for Beginners in 2025 - Best of Lot

Hello guys, if you are interested in Crypto currencies like Bitcoin and Ethereum, then you've probably heard about Blockchain. Unless you're living under a rock . I'm talking about this new technology that offers what cryptocurrencies were most dangerous about… safety. With Blockchain, transaction safety is a must every time. Big companies invest big stacks of money in finding experts in this field. A blockchain expert's salary can go as high as $150,000 per year. So yeah, if you were thinking of learning about Blockchain, this is the right time to do so.

Top 6 Docker Courses for Java and Microservices Developers in 2025 - Best of Lot

Hello Java programmer, if you want to learn Docker and looking for the best Docker Courses from Java and Spring Boot developer point of view, then you have come to the right place. Earlier, I shared free Spring Boot courses and Docker courses, and in this article, I will share the best Docker courses for Java and Spring developers. Java is one of the most popular and widely used programming languages. It is an evergreen programming language. For Java developers, Docker is a game-changer. Docker is emerging rapidly, and it's now one of the most essential tools for all kinds of programmers, and there are reasons for it like Docker makes both development and deployment easier. 

Top 5 Free Courses to crack AWS Solution Architect Certification in 2025 - Best of Lot

A professional certificate speaks louder than a typical CV. Not all certificate holds worth, but some professional certificate does! AWS (Amazon web services) Solution architect associate is one of the most prestigious certifications. There is a lot of demand for AWS certified Solution architects as many companies seek experts who can manage their AWS assets. Amazon also ensures that their partners have certified AWS professionals which further fuels the demand for AWS certification. Given the future of Software development is on the cloud and sooner or later most of the companies will move to the different cloud platforms, particularly AWS gave it's the most popular public cloud, investing your time on acquiring AWS certification can really boost your profile in 2025. 

Top 7 Courses to Learn PyTorch and Keras for Beginners in 2025 - Best of Lot [UPDATED]

Hello guys, if you want to learn PyTorch and Kearas from scratch and look for the best PyTorch and Keras online courses, you have come to the right place. In the past, I have shared the best machine learning courses and best TensorFlow courses, and today I will share the best Keras and Pytorch courses for beginners and experienced programmers. PyTorch and Keras are two deep learning libraries developed by two big companies, Facebook and Google, aiming to facilitate the creation of deep learning applications like face recognition and self-driving cars, and so on.

Top 5 Computer Vision and OpenCV Courses to Learn in 2025 - Best of Lot

Hello guys, if you want to learn Computer Vision and OpenCV and look for the best computer vision online courses from Udemy, Coursera, and Pluralsight, you have come to the right place. Earlier, I have shared the best online courses to learn Python, Data Science, and Machine Learning from Coursera and Udemy, and in this article, I am going to share the best online training courses to learn both Computer Vision and OpenCV. The list includes courses for beginners and experienced programmers who want to learn the advanced concept of Computer Vision and Open CV.  It's one of the most existing fields of Machine Learning and Artificial Intelligence and has uses across industries like object detection, self-driving cars, robotics, and much more.

Top 5 Online Courses to learn Design Patterns in JavaScript in 2025 - Best of Lot

If you are a JavaScript web developer and want to learn design patterns to further improve your coding and development skills and looking for the best design pattern courses in JavaScript, then you have come to the right place. Earlier, I have shared the best JavaScript courses for beginners. Today, I will share the best courses to learn Design Patterns in JavaScript from Udemy, Pluralsight, Udacity, and LinkedIn Learning. These are truly great online courses that you can join to learn this valuable skill and become a better JavaScript developer. 

3 Books and Courses to Learn RESTful Web Services using Spring and Java in 2025 - Best of Lot

Hello guys, if you know the Spring framework, then there is a good chance that you have heard about the classic Spring in Action book by Craig Walls. It's one of the best books to learn Spring, and many Java developers, including me, have learned Spring from that. But, even though the Spring in Action 5th Edition is one of the best books to learn Spring framework, it's just not enough to learn the intricacies of developing a modern, full-featured RESTful Web Service using Spring Framework. It does have a chapter on developing RESTful Web Services. It nicely explains concepts like @RestController, @ResponseBody, @ResponseStatus, HTTP message converters, content negotiation, but that barely touches the surface of developing a production-quality RESTFul Web Service.

Top 10 Java Module Tutorials and Courses to Learn in 2025 - Best of Lot

It's been more than a couple of years or so since JDK 9 was launched, and the new year is probably the best time to learn Java 9 and get yourself familiar with new features and enhancements on existing APIs. The highlight of the JDK 9 release was Project Jigsaw or Module system. The Java 9 Platform Module System allows Java to move forward by modularizing the JDK as well as adding modules as first-class citizens to Java, but that's not the only thing to look forward to, there are many small changes that are very useful in day-to-day coding.

Top 5 Online Courses to Learn Natural Language Processing (NLP) in 2025 - Best of Lot

Hello guys, if you want to learn Natural Langauge Processing (NLP) and looking for the best online training courses then you have come to the right place. Earlier, I have shared the best courses to learn Data Science, Machine Learning, Tableauand Power BI for Data visualization and In this article, I'll share the best online courses you can take online to learn Natural Langauge Processing or NLP.  These are the best online courses from Udemy, Coursera, and Pluralsight, three of the most popular online learning platforms. They are created by experts and trusted by thousands of developers around the world and you can join them online to learn this in-demand skill from your home.

Top 5 Free Scikit- Learn Courses to Learn Online in 2025 - Best of Lot

Let’s assume you have some knowledge in python language and want to have a career in either deep learning or machine learning, they’re no best libraries to learn than scikit learn. This library is widely used and contains tons of algorithms created by python but can perform various machine learning tasks like classification and regression. In the past, I have shared the best free Machine Learning courses as well as best courses to learn the best Machine learning libraries like TensorFlow, NumPy, Scikit Learn, Kears, and Panda and in this article, I am going to share the best free resources to learn 

Top 5 Courses to Learn Responsive Web Design in 2025 - Best of Lot

Hello folks, Responsive web design is one of the essential skills to become a frontend web developer, a web designer, and even a full stack developer. If you are interested in learning Responsive web design and looking for the best online training courses, then you have come to the right place. I have shared the best online courses to learn UI/UX design, HTML 5, CSS 3, and Photoshop in the last few articles. This article will share the best online courses to learn Responsive web design from sites like Udemy, Pluralsight, Coursera, and other popular online portals.  

5 Free Online Courses for AWS Solution Architect Professional Exam in 2025 - Best of Lot

Hello folks, if you are preparing for the AWS Certified Solution Architect Professional exam and looking for some free online courses then you have come to the right place. In the past, I have shared free and best online courses to prepare for  AWS Cloud Practitioner, AWS Developer, AWS Architect Associate, and SysOps Administrator certification, and today I am going to share free online courses to prepare for the AWS Solution Architect Professional certification exam in 2025. The AWS Solution Architect Professional Exam is one of the most reputed and most challenging AWS certification exams. For this exam, you have to be ready enough to answer questions from any corner of AWS.

Review — Is tryExponet.com Good Place for System Design Interview Prep in 2025?

Hello guys, its every developer’s dream to get a SDE job on FAANG company. I dreamed it too and having gone through interview on Google, Microsoft and Amazon, I know a thing or two about these interviews.  Many developer fail these interview either because of data structures and algorithms or because of System Design. Even for experienced developer cracking a system design interview is not easy. It requires patience, perseverance and dedication to learn the intricacies of system design and acquire knowledge to crack interview.

Top 5 Udemy Courses to Learn Distributed Systems in 2025

Hello guys, Distributed systems are the backbone of modern applications, enabling scalability, fault tolerance, and high availability. Whether you’re building microservices, cloud applications, or real-time systems, understanding distributed systems is crucial. If you want to learn Distributed System in 2025 and looking for resources then you have come to the right place. Earlier, I have shared  best System Design Books, System Design Questions and best Places to learn System Design and in this article, I am going to share best Distributed System courses from Udemy, one of my favorite place to learn programming and technical stuff. 

Is System Design Interview Inside Guide Vol 1 and 2 Book Worth Reading in 2025? Review

 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, 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

Top 5 System Design and Coding Interview Substack Newsletters in 2025

Hello guys, if you want to learn System design then there are many ways you can start. For example, you can start with reading a System Design book, or joining an online course, but if you want to keep yourself updated and believe in constant learning then there is no better way then subscribing to a System Design Newsletter. When it comes to System design newsletter you can find many newsletter online, just open your LinkedIn and you will see a post popping here or there but you cannot subscribe to all of them as it doesn't make sense. A better strategy is to subscribe only the best newsletters so that you doesn't get overwhelmed but also keep learning useful concepts and new tech trends. 

Top 10 Free Core Spring, Spring MVC, and Spring Boot Courses for Beginners in 2025 - Best of Lot

Hello guys, if you want to learn Spring Framework, Spring MVC and Spring Boot then you are at the right place. In this post you will find the best free courses to learn Spring Framework, Spring MVC and Spring Boot in 2025. I have been sharing a lot of resources like books and courses recently and when I published my list of Top 5 courses to learn Spring and Hibernate, many of my readers asked about a similar list of free courses to learn Spring Framework like Core Spring, Spring MVC, Spring Security, and Spring Boot. That request was always back in my mind but I couldn't get time to put together a list, which I can share with you guys, but today is the day. In this list, I have compiled some of the best online free courses to learn Spring Framework from scratch, online at your own pace. 

10 Best System Design Interview Courses for Software Engineers in 2025

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 BooksFree 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 2025. 

3 ways to Learn Java Programming in 2025? Books, Courses, and Projects

Hello guys, if you want to learn Java and wondering what is the best way to learn Java in 2025 then you have come to the right place. In the past, I have shared many useful resources to learn Java programming and development like the 2025 Java Developer RoadMapbest Java coursesbest Java books, and this list of best websites to learn Java for FREE, and in this article, I will tell you the best way to learn Java in 2025. Learning Java programming is quite rewarding and I can say that it was my best decision to learn Java 20 years ago. It opens doors to many opportunities in software development and lucrative jobs like Java developers on Investment banks like JP Morgan, UBS, Citibank, Barclays, and more. 

Top 10 Online Courses to Learn Python in 2025 - Best of Lot

Hello guys, if you want to learn Python programming language in 2025 and are looking for the best Python courses, you have come right. There are a lot of resources to learn Python on the web, including free and paid. In the past, I have also shared a lot of accessible sources like free books,  tutorialscourses, specialization, and certifications. Still, many of you asked for more comprehensive and advanced Python courses to master this essential programming skill in 2025. We have selected a few advanced Python online training courses from platforms like UdemyCoursera, edX, ZTM Academy, and Pluralsight to help you learn Python from the best resources. 

10 Best Udemy Courses of Stephen Grider to Learn Tech Skills in 2025

Hello guys, if you are looking to learn web development or app development then there is a good chance that you may heard about Stephen Grider, one of the best Udemy instructor when it comes to teaching web development technologies. In the past, I have shared best online courses by Jose Portilla, Maximillian SchwarzMuller, Stephane Maarek and Brad Traversy and in this article, I am going to share best online course by Stephen Grider. But, First things first. before I tell you about the 10 best Udemy courses of Stephen Grider, let me tell you who the man really is.

Top 5 Python Courses for Data Science and Machine Learning in 2025 - Best of Lot

We all know what Python is, right? It is a high-level, general-purpose programming language with enhanced readability. The syntax is also well-constructed and has an object-oriented approach. This will enable programmers to write clear and logical code for small and large projects. Data Science can be broadly defined as a field that extracts insights from structured and unstructured data using scientific methods and algorithms. These insights can then be applied across various domains and fields. It can be used for increasing sales, optimizing workflow, cash flow, etc.

Top 6 Free Courses to learn PHP and MySQL in 2025 [Updated] - Best of lot

If you want to build web applications quickly like overnight or over the weekend, then PHP and MySQL are the right choices and because of this power, they are also the best language for freelancing and startups where a quick turnaround time is required. PHP and MySQL are incredibly powerful open source technologies that allow programmers and web developers to create functional websites and apps that go way beyond basic HTML. PHP is specially designed to generate interactive and dynamic websites and is also known as the server-side scripting language, while MySQL is one of the leading relational databases along with Oracle and Microsoft SQL Server.

Top 5 Free Courses to Learn C# (C-Sharp) in 2025 - Best of Lot

Many people underestimate the power of C# and never think highly of it when they talk about programming languages. Still, the truth is that C# is one of the popular programming languages of today's world, just behind JavaScript, SQL, and Java on StackOverFlow's Developer Survey for the last couple of years. There are a lot of jobs and opportunities available for experienced C# developers. It's one of the critical languages for developers working with Microsoft technologies like Windows and SQL Server. It is also one of the most popular programming languages for developing desktop GUI, surpassing Java Swing entirely in the last couple of years. I have seen many big investment banks switched from Swing to C# for their GUI development work.

Top 7 Free Selenium Courses for Beginners to Learn Online in 2025 - Best of Lot

Testing is an integral part of software development. We have long relied on manual testing by testers and QA professionals to ship quality software and find bugs, but that's not sustainable anymore. There is an increased focus on automation testing nowadays, and Selenium is leading its web drivers. If you don't know Selenium, it's a free automation testing tool for web applications. It can work with different web browsers like Chrome, Firefox, Internet Explorer, and Opera and simulate human-like behavior. Using Selenium, you can programmatically interact with all the other elements on a webpage. You can click on them, input text, extract text, and more.

Top 10 Free Udemy Courses to Learn Coding and Web Development in 2025 - Best of Lot

When I was a little kid, I remember reading somewhere that coding will be the language of the future. I was intrigued. What was this new language that I didn't know about and nobody around me spoke? How was it going to be the language of the future? Before we get to the 10 free Udemy courses that will teach you coding, let me tell you a little more about what coding is.  

Top 5 Free Courses to learn Salesforce in 2025 - Best of Lot

Hello there, If you want to learn the Salesforce platform and looking for some free online Salesforce courses, then you have come to the right place. Earlier, I shared the best online practices for  Salesforce DeveloperAdministrator, and App Builder certification. Today, I will share free Salesforce courses beginners can use to learn this handy platform and add an in-demand skill to their resume. The Salesforce platform is a unique platform for custom application design, analytics features, and new features.

Top 5 Free Courses to Learn Ruby on Rails for Beginners in 2025 - Best of Lot [UPDATED]

Hello guys, welcome to this post, here you will find some of the best free courses to learn Ruby programming language and Ruby on Rails framework online from Udemy. If you don't know what Ruby is and what is Rails framework is, then let me tell you that it's one of the simplest programming languages with little to no syntax. If you are new to programming or never coded before, then also developing a Ruby application will be much more comfortable than choosing any other programming language like Python or Java

Top 6 Online Course to learn from Java 9 to Java 23 in 2025 - Best of Lot

Hello guys, even though Java 15 is available now, many developers are still on Java 8 and not really caught up with changes in Java 9, 10, 11, 12, 13, or Java 14. If you are also in the same boat and want to start with Java 9 features, you have come to the right place. This article will share some of the best online courses to learn changes in Java 9, 10, 11, and later add more classes for Java 12, 13, 14, and 15. These JDK releases are packed with powerful features like modules, API enhancements like factory methods for an immutable list, set, and map, some changes on stream API and optional class, new features on process API, etc. 

5 Free Courses to Crack GCP Professional Cloud DevOps Engineer Exam in 2025 - Best of Lot

If you are preparing for Google Cloud Professional DevOps Engineer certification  in 2025 and looking for free online Google cloud DevOps Engineer courses then you have come to the right place. In the past, I have shared the best Google Cloud courses and best DevOps Courses,  as well as the best online training courses to pass cloud engineer, data engineer, and cloud architect certifications, but my readers kept asking for free online courses on Google Cloud, particularly for DevOps engineer certification, and today, I am going to share free GCP Cloud DevOps Engineer certification courses for both beginners and experienced cloud professionals.

Top 8 Free Courses to Learn Web Design in 2025 - Best of Lot

Hello guys, if you want to become a web designer and look for free online courses to learn web design in 2025, you have come to the right place. In the past, I have shared the best free online resources to learn key web development skills like HTMLCSS, JavaScriptBootstrap, and today, I am going to share the best free resources to learn web design and development.  These free courses have been created by expert instructors like Jonas Schmedtmann, and they are from websites like Udemy, Coursera, and edX.  You can use these free online courses to learn these valuable skills and become a web designer and developer.

Top 5 Courses to Learn Angular for Web Development in 2025 - Best of Lot

Hello guys, if you want to learn Angular in 2025 and looking for the best Angular courses then you have come to the right place. In the past, I have shared many resources to learn and master Angular like the best Angular books as well as free courses to learn Angular but many of you asked me to share more comprehensive and in-depth Angular courses and here we are with the list of the best Angular online courses to learn in 2025. These are comprehensive, in-depth, and up-to-date Angular courses, curated from popular websites and online courses platforms like Udemy, Pluralsight, Coursera as well as interactive platforms like Educative.