What is CyclicBarrier Example in Java 5 – Concurrency Tutorial

What is CyclicBarrier in Java

CyclicBarrier in Java is a synchronizer introduced in JDK 5 on java.util.Concurrent package along with other concurrent utility like Counting Semaphore, BlockingQueue, ConcurrentHashMap, etc. CyclicBarrier is similar to CountDownLatch which we have seen in the last article  What is CountDownLatch in Java and allows multiple threads to wait for each other (barrier) before proceeding. The difference between CountDownLatch and CyclicBarrier is also a very popular multi-threading interview question in Java. CyclicBarrier is a natural requirement for a concurrent program because it can be used to perform the final part of the task once individual tasks are completed.

What is happens-before in Java Concurrency? An example

A couple of days ago, one of my readers messaged me on LinkedIn about a Java interview question he has recently faced - what is the happens-before relationship in Java concurrency? What is the benefit of it, and how exactly it works? He kind of has some ideas about that its related to the Java Memory Model and provides some sort of visibility guaranteed but couldn't explain with conviction to his interviewer, particularly with a code example and was a bit disappointed. He then asked me if I can write an article about it. I said you should have read the Java concurrency in Practice book before the interview, that would have helped, but nonetheless, I liked the idea to just provide a quick overview of what is the happens-before relationship between threads in Java.