What is Blocking Deque in Java? How and When to use BlockingDeque? Example Tutorial

Hello friends, we meet again here today on our journey to Java. Before we continue forward, let me inform you guys that today's topic is in continuation of our Java Deque topic. If any of you guys have not read the Java Deque tutorial, go ahead and read that one first. Though there is no such limitation of this article, it is recommended to have gone through the basics of Deque and our previous post. So, I guess now we will continue our Deque topic and today we will discuss something very interesting. Today we are gonna jump into the advanced topic of Deque and how we can leverage the functionality Java has provided for a better and more robust application building.

Java CountDownLatch Example for Beginners - [Multithreading Tutorial]

Hello Java programmers, the CountDownLatch is an important concurrency utility class that was added in JDK 1.5 to facilitate inter-thread communication without using wait and notify methods, but unfortunately, many Java developers still struggle to understand and use this powerful tool. In this article, you will learn what is CountDownLatch and how to use it to write better concurrent applications in Java. You can use the CountDownLatch if you are spawning multiple threads to do different jobs and want to know when exactly all tasks are finished so that you can move to the next stage. In other words, you can block a thread until other threads complete their task. 

Java CyclicBarrier Example for Beginners [Multithreading Tutorial]

This is the second part of my concurrency tutorial, in the first part, you have learned how to use CountDownLatch and in this part, you will learn how to use CyclicBarrier class in Java. CyclicBarrier is another concurrency utility introduced in Java 5 which is used when a number of threads (also known as parties) want to wait for each other at a common point, also known as the barrier before starting processing again. It's similar to the CountDownLatch but instead of calling countDown() each thread calls await() and when the last thread calls await() which signals that it has reached the barrier, all threads started processing again, also known as a barrier is broken. 

25 Examples of ConcurrentHashMap in Java

The java.util.ConcurrentHashMap is one of the most important classes of JDK. It was introduced in JDK 1.5 along with other concurrent collection classes like CopyOnWriteArrayList and BlockingQueue. Ever since then, it has been a workhorse in concurrent Java applications. It won't be an exaggeration If I say there is hardly any concurrent Java application that has not used ConcurrentHashMap yet. The class was another implementation of java.util.Map and a popular hash table data structure with concurrency inbuilt. This means you can also pass a ConcurrentHashMap to a method that is expecting a java.util.Map object. It was made scalable by dividing the whole map into a different segment, known as concurrency level, and then allowing threads to modify segments concurrently.

How ThreadLocal variables works in Java? Explained

Hello guys, ThreadLocal variable is an interesting concept and class from Java API. Not many developer knows about it and very few know how to use it correctly. A couple of years ago it was also a popular Java interview questions for experienced developer but over the years, it lost the popularity as more and more people are now asking about Phaser, CompletableFuture, ForkJoinPool, and other newly added concurrency utilities. ThreadLocal variables, as name suggests is local to thread, which means every thread has there own copy. This means they don't need to look at the main memory when they want to use that variable and best thing is that the variable is not even shared between threads so no locking or synchronization is needed. 

How to run Threads in an Order in Java - Thread.Join() Example

Hello Java programmers, if you need to execute multiple threads in a particular order, for example if you have three threads T1, T2 and T3 and we want to execute them in a sequence such that thread 2 starts only when first thread finishes it job and T3 starts after T2, but with multithreading in Java there is no guarantee. Threads are scheduled and allocated CPU by thread scheduler which you cannot control but you can impose such ordering by using Thread.join() method. When you start a thread its not guaranteed that which thread will start first and whether the thread started first will finish first, if your application's logic depends upon a sequence its better to do all those operation on single thread because if all code is confined to one thread it will execute in order they were written provided some JIT optimization.

How to Create, Start, and Stop a New Thread in Java? [Example Tutorial]

One of the most important tasks for a Java developer is to learn multi-threading and learn it correctly. There are more Java developers who know multi-threading incorrectly than the programmer who doesn't know at all. In order to learn it correctly, you need to start it from scratch, means the most fundamental concepts of multithreading like how to create create, start, and stop a new thread in Java. I am sure you already know that as you have done that a lot of time but it's worth remembering few facts to not repeat the mistakes many programmers do when they write multithreading code in Java. 

How to use CountDownLatch in Java? Example

CountDowaLatch is a high-level synchronization utility that is used to prevent a particular thread to start processing until all threads are ready. This is achieved by a countdown. The thread, which needs to wait for starts with a counter, each thread make the count down by 1 when they become ready, once the last thread call countDown() method, then the latch is broken and the thread waiting with the counter starts running. CountDownLatch is a useful synchronizer and is used heavily in multi-threaded testing.

How to use CompletableFuture in Java? Example Tutorial

Hello friends, we meet again today on our journey to Java. So I hope you guys are excited about this Java concurrency lesson. Let me ask you guys one thing before we proceed. Do you guys ever wonder about the future? At some point in time, all of you must have thought about it and wondered about different kinds of outcomes. Well, our Java program also wonders about its future tasks so, let us learn today something similar to that! First of all, before jumping onto what a CompletableFuture is, let us first know what a Future in Java is? For guys who know this beforehand, just refresh the concept and for everyone else, let’s understand what it is.

Difference between CountDownLatch vs CyclicBarrier in Java Multithreading

Difference between CountDownLatch and CyclicBarrier in Java
Both CyclicBarrier and CountDownLatch are used to implement a scenario where one Thread waits for one or more Thread to complete their job before starting processing but there is one difference between CountDownLatch and CyclicBarrier in Java which separates them apart and that is, you can not reuse the same CountDownLatch instance once count reaches to zero and latch is open, on the other hand, CyclicBarrier can be reused by resetting Barrier, Once the barrier is broken.

When to use notify() and notifyAll() in Java

As a programmer, you must not rely on any particular selection algorithm or treatment of priorities, at least if you are trying to write a Java program that is platform-independent. For example, because you don't know what order threads in the wait set will be chosen for resurrection by the notify command, you should use notify (as opposed to notify all) only when you are absolutely certain there will only be one thread suspended in the wait set. If there is a chance more than one thread will be suspended in the wait set at any one time, you should probably use notify all.

Otherwise, on some Java virtual machine implementations, a particular thread may be stuck in the wait set for a very long time. If a notify always selects the most recent arrival from the wait set and the wait set always contains multiple threads, some threads that have been waiting the longest may never be resurrected.