Top Most ReentrantLock Example in Java, Difference between synchronized vs ReentrantLock

ReentrantLock in Java is added on java.util.concurrent package in Java 1.5 along with other concurrent utilities like CountDownLatch, Executors and CyclicBarrier. ReentrantLock is one of the most useful addition in Java concurrency package and several of concurrent collection classes from java.util.concurrent package is written using ReentrantLock, including ConcurrentHashMap, see How ConcurrentHashMap works in Javafor more details. Two key feature of ReentrantLock, which provides more control on lock acquisition is trying to get a lock with ability to interrupt, and a timeout on waiting for lock, these are key for writing responsive and scalable systems in Java. In short, ReentrantLock extends functionality of synchronized keyword in Java and open path for more controlled locking in Java. 

In this Java concurrency tutorial we will learn :

• What is ReentrantLock in Java ?
• Difference between ReentrantLock and synchronized keyword in Java?
• Benefits of using Reentrant lock in Java?
• Drawbacks of using Reentrant lock in concurrent program?
• Code Example of ReentrantLock in Java?

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Top Most How to Join Multiple Threads in Java - Thread Join Example

Join method from Thread class is an important method and used to impose order on execution of multiple Threads. Concept of joining multiple threads is very popular on  mutithreading interview question. Here is one of such question, “You have three threads T1, T2 and T3, How do you ensure that they finish in order T1, T2, T3 ?. This question illustrate power of join method on multithreaded programming. Unlike classical thread questions like difference between wait and sleep methodor solving producer consumer problem in Java, This one is bit tricky. You can do this by using join method, by calling T1.join() from T2 and T2.join() from T3. In this case thread T1 will finish first, followed by T2 and T3. In this Java multithreading tutorial we will have a closer look on join method with a simple example. Idea is to illustrate how join method works in simple words. By the way from Java 5 onwards you can also use CountDownLatch and CyclicBarrier classes to implement scenarios like one thread is waiting for other threads to finish there task.

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