Memory Visibility with the volatile Keyword

Snippet

Memory Visibility with the volatile Keyword

The volatile keyword ensures that changes to a variable are always visible to all threads immediately. It prevents threads from caching the variable locally, ensuring they always read the latest value from main memory.

snippet.java
java
public class SharedFlag {
    private volatile boolean active = true;
 
    public void stop() { active = false; }
 
    public void work() {
        while (active) { /* perform task */ }
    }
}

Breakdown

private volatile boolean active

Ensures any write to 'active' is visible to other threads reading it without needing explicit synchronization.

while (active)

The loop will correctly terminate even if another thread calls stop(), as it always checks the main memory.

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Memory Visibility with the volatile Keyword

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