Difference between ReentrantLock and synchronized in Java

Deep Dive in a popular Java concurrency and multi-threading interview question

In concurrent programming, synchronization is essential to ensure that multiple threads can safely access shared resources without causing data inconsistencies or race conditions.

In Java, there are two primary mechanisms for achieving synchronization: ReentrantLock and the synchronized keyword.

The ReentrantLock and synchronized lock both serve the purpose of allowing exclusive access to critical sections of code, but they differ in terms of flexibility, performance, and the level of control they provide to developers.

Understanding the differences between these two synchronization approaches is crucial for Java developers aiming to build efficient and reliable concurrent applications.

In the past few posts, I have shared popular Java interview questions like,, How ConcurrentHashMap work in Java? Why String is Immutable, why wait() and notify() is called from synchronized context, and difference between List, List<Object> and in this article, I will share a popular multithreading questions from interviews.

We will explore the key distinctions between ReentrantLock and the synchronized lock in Java.

We will delve into their usage, advantages, limitations, and recommended scenarios for each to help you make informed decisions when employing synchronization mechanisms in your Java applications.

Let's dive into the comparison of ReentrantLock and synchronized to gain insights into which approach best suits your concurrent programming needs.

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Difference between ReentrantLock vs synchronized lock in Java?

Here are key differences between a ReentrantLock and synchronized keyword lock in Java for easy reference

1. Scope

The lock acquired by synchronized block or method cannot go beyond a single method.

Thread has to leave the lock one it goes out of method, but Lock interface or ReentrantLock allows you to extend locking scope beyond one method.

Though, It's possible to call lock() and unlock() in separate methods.