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Understanding the Java Memory Model: Making Sense of Multi-threaded Programming
When you write a Java program that uses multiple threads, you need to understand how these threads work with memory. This is where the Java Memory Model (JMM) comes in. The JMM is a set of rules that control how Java programs access memory when multiple threads are running.
In this article, we’ll break down the Java Memory Model in simple terms. You’ll learn what it is, why it matters, and how it helps your multi-threaded programs run correctly.
What is the Java Memory Model?
The Java Memory Model (JMM) describes how threads in Java interact with memory. It defines rules for:
- Visibility: When one thread changes a value, how and when other threads see that change
- Ordering: The sequence in which memory operations happen
- Atomicity: Operations that happen all at once without being interrupted
Before we dive deeper, let’s understand why these rules are needed.
Why Do We Need the Java Memory Model?
Modern computers have complex memory systems. There are multiple levels of cache between the CPU and main memory. Each CPU core might have its own cache. When multiple threads…