How to implement Command Design Pattern in Java with Example

Hello guys, it's been a long since I have shared a Java design pattern tutorial. I did share some courses to learn design patterns but haven't really talked about a particular design pattern in depth. So, today, we'll learn one of the important design pattern, which is often overlooked by Java developers. Yes, I am talking about the Command Pattern which can help you write flexible, loosely coupled code for implementing actions and events in your application. In simple words, the command design pattern is used to separate a request for action from the object which actually performs the action. This decoupling between Invoker and Receiver objects provides a uniform way to perform different types of actions. This decoupling is achieved using a Command object, which is usually an interface with methods like execute(). 

How to sort an Array in Java? Ascending and Descending Order Example

As a Java programmer, quite often you would need to sort array in Java luckily java.util.Arrays class provides several utility methods to sort an array in Java. You can sort different types of array in Java like array of primitive data types, object or int, String, etc. Arrays are in java.util package and exposed all sorting related methods as static utility functions. you can access sort() as Arrays.sort() and just pass your array and it will sort that array object by comparing them in the order implemented in the compareTo() method if the class implements Comparable interface. You can also sort arrays in ascending order, descending order, or any custom order defined by the custom comparator in Java.

How to loop through an Array in Java? Example Tutorial

Hello there, If you want to loop over an array in Java but not sure how to do that then you have come to the right place. Earlier, I have shared many Java array tutorials and the best Java courses for beginners, and today, I am going to teach you how to iterate over an array in Java. There are multiple ways to loop over an array in Java, like you can use a for loop, an enhanced for loop, a while loop, or a do-while loop. Since while and do-while needs a condition to terminate they often depend upon the content of the array like stop when the current element is null or even or odd etc. If you just want to iterate over an array to access each element like loop over an array and print each entry then you should use either for loop or the enhanced for loop.

How to declare and initialize a List with values in Java (ArrayList/LinkedList) - Arrays.asList() Example

Hello guys, today, I am going to share with you a useful tip to initialize a List like ArrayList or LinkedList with values, which will help you a lot while writing unit tests and prototypes. Initializing a list while declaring is very convenient for quick use, but unfortunately, Java doesn't provide any programming constructs like the collection literals of Scala, but there is a trick which you can use to declare and initialize a List at the same time. This trick is also known as initializing a List with values. I have used this trick a lot while declaring list for unit testing and writing demo programs to understand an API etc and today I'll you'll also learn that.

How to implement Skip List in Java? Example Tutorial

Hello friends, we meet again today. hope you all are excited and ready for today's journey. Today, we are gonna learn something that is not very common. It is used not very common, but, if used, it is a great strength to our time complexity reduction. So, what's the wait? Let's start! So, suppose we have a linked list with us which has 10 million records. Now, for searching a particular node, the time taken would be O(N). Where N is the size of the list. Similarly, the time taken for deletion of a Node, Insertion at a particular Node will also take O(N) time. Can we reduce it?

Top 5 Websites to Learn Java Coding for FREE - Best of lot

Hello guys, if you want to learn Java Programming and looking for the best websites to learn Java coding for free then you have come to the right place. In the past, I have shared the best Java courses and books, today, I am going to share free websites to learn Java Programming for free. being the author of a Java blog and programmer I often receive questions like how to improve my coding skills?,  or how do I learn to code in Java?, or I am having difficulty solving programming problems, please help, etc. This is mostly from programmers who have just started programming or computer science graduates with a programming degree or even some programmers with a year or two in Job.

Can a Non Static Method Access a Static Variable/Method in Java?

"Can a non-static method access a static variable or call a static method" is one of the frequently asked questions on the static modifier in Java, the answer is, Yes, a non-static method can access a static variable or call a static method in Java. There is no problem with that because of static members i.e. both static variable and static methods belong to a class and can be called from anywhere, depending upon their access modifier. For example, if a static variable is private then it can only be accessed from the class itself, but you can access a public static variable from anywhere.

How to find If Linked List Contains Loop or Cycle in Java? Example Solution

Write a Java program to check if a linked list is circular or cyclic,  and how do you find if a linked list contains loop or cycles in Java are some common linked list related data structure interview questions asked in various Java Interviews. This is sometimes asked as a follow-up question of basic linked list questions like inserting an element at the beginning, middle and end of a linked list or finding the length of linked list. In order to solve linked list related algorithmic questions in Java, you need to be familiar with the concept of singly linked list, doubly linked list, and circular linked list. Until stated specifically, most questions are based on a singly linked list. For those who are not familiar with the linked list data structure, its a collection of nodes.

How to create Tabs UI using HTML, CSS, jQuery, JSP and JavaScript? Example

JSP is still a popular technology for developing view part of Struts and Spring-based Java applications, but unfortunately, it doesn't have rich UI support available in GWT, or any other library. On another day, we had a requirement to display HTML tables inside tabs, basically, we had two tables of different data set and we need to display them in their own tabs. Users can navigate from one tab to another, and CSS should take care of which tab is currently selected, by highlighting the active tab. Like many Java developers, our hands-on HTML, CSS, and JavaScript are a little bit tight than a web guy, and since our application is not using any UI framework, we had to rely on JSP to do this job.

Top 5 books to Learn Object Oriented Programming and Design - Must Read, Best of Lot

The OOP or Object Oriented Programming is one of the most popular programming paradigms which helps you to organize code in the real-world system. It's a tool that allows you to write sophisticated software by thinking in terms of objects and relationships. Unlike its predecessor procedural Programming paradigm, which is implemented most notably by C, which solves the problem and complete task by writing code for computers, the OOP style of programming allows you to think in terms of real-world objects which have both state and behavior. You can view anything as objects and then find their state and behaviors, this will help you to simulate that object in code.

How to use Adapter Design Pattern in Java with Example

The adapter design pattern in Java, also known as the Wrapper pattern is another very useful GOF pattern, which helps to bridge the gap between two classes in Java. As per the list of Gang of Four patterns, the Adapter is a structural pattern, much like Proxy, Flyweight, Facade, and Decorator patterns in Java. As the name suggests, the Adapter allows two classes of a different interface to work together, without changing any code on either side. You can view the Adapter pattern as a central piece of the puzzle, which joins two pieces, which can not be directly joined because of different interfaces.

What is the Use of Interface in Java and Object Oriented Programming? [Answer]

Many times, I have seen questions like why should we use an interface in Java? If we can not define any concrete methods inside the interface the what is the user of the interface? Or even more common, What is the real use of the interface in Java? I can understand beginners asking this question when they just see the name of the method inside the interface and nothing else. It takes time to realize real goodness or actual use of interface or abstraction in Java or any object-oriented programming. One reason for this is a lack of experience in really modeling something real in the program using object-oriented analysis and design. In this article, I will try to answer this question and give you a couple of reasons to use the interface in your code. If you have a good understanding of Object-oriented basics like Polymorphism, then you know that it allows you to write flexible code.

Difference between Inheritance and Composition in Java and Object Oriented Programming

Though both Inheritance and Composition provide code reusability, the main difference between Composition and Inheritance in Java is that Composition allows reuse of code without extending it but for Inheritance, you must extend the class for any reuse of code or functionality. Another difference that comes from this fact is that by using Composition you can reuse code for even the final class which is not extensible but Inheritance cannot reuse code in such cases. Also by using Composition, you can reuse code from many classes as they are declared as just a member variable, but with Inheritance, you can reuse code from just one class because in Java you can only extend one class because multiple Inheritance is not supported in Java.

java.lang.UnsatisfiedLinkError: no dll in java.library.path - Cause and Solution

"Exception in thread "main" java.lang.UnsatisfiedLinkError: no dll in java.library.path" is one of the frustrating errors you will get if your application is using native libraries like the DLL in Windows or .SO files in Linux. Java loads native libraries at runtime from either PATH environment variable or location specified by java.library.path system property depending upon whether your Java program is using System.load() or java.lang.System.loadLibarray() method to load native libraries. If Java doesn't find them due to any reason it throws "java.lang.UnsatisfiedLinkError: no dll in java.library.path". 

Spring Boot Error - Error creating a bean with name 'dataSource' defined in class path resource DataSourceAutoConfiguration

Hello guys, If you are using Spring Boot and getting errors like "Cannot determine embedded database driver class for database type NONE" or "Error creating a bean with name 'dataSource' defined in class path resource ataSourceAutoConfiguration" then you have come to the right place. In this article, we'll examine different scenarios on which this Spring Boot error comes and what you can do to solve them. The general reason for this error is Spring Boot's auto-configuration, which is trying to automatically configure a DataSource for you but doesn't have enough information. It is automatically trying to create an instance of DataSourceAutoConfiguration bean and it's failing.

Difference between WHERE vs HAVING clause in SQL - GROUP BY Comparison with Example

What is the difference between WHERE and  HAVING clause in SQL is one of the most popular questions asked on SQL and database interviews, especially to beginners? Since programming jobs, required more than one skill, it’s quite common to see a couple of SQL Interview questions in Java and .NET interviews. By the way unlike any other question, not many Java programmers or dot net developers, who are supposed to have knowledge of basic SQL, fail to answer this question. Though almost half of the programmer says that WHERE is used in any SELECT query, while HAVING clause is only used in SELECT queries, which contains aggregate function or group by clause, which is correct.

How to Design Vending Machine in Java - Part 2 [Object Oriented Design Problem with Solution]

This is the second part of the Java tutorial to show how to design Vending Machine in Java. In the first part, we have discussed the problem statement and the solution itself, but unit testing and design document were still pending, which we'll see in this article.  As I said, there are multiple ways to design a Vending machine in Java, for example, you could have easily used state design patterns to implement a vending machine, in fact, it's one of the best examples of State design patterns. Vending machine behaves differently in different states like return a product if the machine is not empty, otherwise, it just returns coins, so it ideally fits in the state design pattern.