Tuesday, May 28, 2019

How to Create a thread-safe ConcurrentHashSet in Java 8? Example

Until JDK 8, there was no way to create a large, thread-safe, ConcurrentHashSet in Java. The java.util.concurrent package doesn't even have a class called ConcurrentHashSet, but from JDK 8 onwards, you can use the newly added keySet(default value) and newKeySet() methods to create a ConcurrentHashSet backed by ConcurrentHashMap in Java. This is better than old tactical solutions like using a concurrent hash map with dummy value or using the set view of the map, where you cannot add new elements. The Set returned by keySet(defaultValue) and newKeySet() methods of JDK 8 is a proper set, where you can also add new elements along with performing other set operations e.g. contains(), remove() etc.

Sunday, May 26, 2019

Top 5 Node.js and Express JS online courses for Web Developers

There is no doubt that JavaScript is the #1 Programming language in the world and Node.js is one of the biggest reason for that. Initially, JavaScript was considered just a client-side scripting language but Node.js has changed all that by allowing developers to create dynamic web pages on the server side using JavaScript. It is also rated as the most popular framework of 2017 on StackOverflow Developers survey. The most important benefit of Node.js is that it allows you to build a full stack application based on just one language, JavaScript. This is especially useful for start-ups which put a lot of emphasis on being able to iterate early and often.

Friday, May 24, 2019

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 Spring framework. The @Autowired annotation is used for auto-wiring in Spring framework. If you don't know, autowiring is a process on which Spring framework figure out 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.

What is the Role of InternalResourceViewResolver in Spring MVC? Interview Question

Earlier, I have explained to you about how Spring MVC works internally and how it process HTTP request coming to your web application. One of the important parts of that processing was view resolution, which is handled by the ViewResolver interface. In this article, you'll learn more about it by explaining the InternalResourceViewResolver class. The InternalResourceViewResolver is an implementation of ViewResolver in Spring MVC framework which resolves logical view name e.g. "hello" to internal physical resources e.g. Servlet and JSP files e.g. jsp files placed under WEB-INF folder. It is a subclass of UrlBasedViewResolver, which uses "prefix" and "suffix" to convert a logical view name returned from Spring controller to map to actual, physical views.

Tuesday, May 21, 2019

How to find all Checked checkboxes in jQuery? Example Tutorial

Hello guys, suppose you have multiple checkboxes in your HTML page and you want to retrieve all checkboxes which are checked? How will you do that in jQuery? Well, you can use the pseudo selector like :checked to get all checked checkboxes. This selector checks for the checked property of checkbox and returns only those checkboxes which have this property. For example, following jQuery selector will return all the checkboxes which are checked:

$('input[type=checkbox]:checked')

In this, we are first selecting all input elements where type is a checkbox and then adding: checked to filter only those which are checked.

Monday, May 20, 2019

Top 10 ConcurrentHashMap Questions from Java Interviews

The ConcurrentHashMap class part of concurrent collections package added on JDK 1.5 which contains utility classes like BlockingQueue, CopyOnWriteArrayList, CopyOnWriteArraySet etc. It is a replacement of synchronized hash-based map implementations e.g. Hashtable and synchronized HashMap. It implements Map and ConcurrentMap (a sub-interface of Map) interface which allows you to store key-value pairs. The class is similar to HashMap or Hashtable but it's more scalable and the right fit for concurrent Java application. Unlike Hashtable which achieves its thread-safety by compromising the scalability, ConcurrentHashMap uses advanced techniques e.g. dividing the map into segments to remain thread-safe and scalable at the same time.

Saturday, May 18, 2019

Entuware or Whizlabs? Which Exam Simulator Should you Buy for Java Certifications (OCAJP, OCPJP, and Others)?

I often receive queries from Java certification aspirants about exam simulators like whether should I go for Whizlabs or Enthuware, which one is better? If I have to buy just one exam simulator, which one would you recommend, Whizlabs or Enthuware? I thought to answer all those questions in a blog post and here you go. To be honest with you both of them are really high-quality test simulators and whichever you buy, you will do well on actual exams. But, as a programmer, I really like to analyze the situation, I compare pros and cons of each of them before I buy one of them. Since I have used both of them in the past I am sure about that in quality, they are neck to neck there, but here are couple of things which you can consider before buying Java certification simulator from Whizlabs or Enthuware

Thursday, May 16, 2019

Java 9 Example - Factory Methods for Collection - Creating Unmodifiable List, Set, and Map

Hello guys, this is my first article in Java 9 features on this blog and today you'll learn about my favorite feature "factory methods for collection", which is introduced as part of JEP 269. The JEP stands for JDK enhancement proposal. If you have worked in Groovy or Kotlin then you know that how easy is to create the list with elements using collection literals e.g. to create a list of 1, 2, 3 you can simply write val items = listOf(1, 2, 3). Unfortunately, Java doesn't support that yet but things have been improved with the factory methods for collection in JDK 9 and it's almost like that. JDK has added static factory methods like of() on to basic Collection interfaces which you can use to create a list of items.

Tuesday, May 7, 2019

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