Explain the purpose and behavior of the volatile keyword in Java.

In Java, the keyword volatile is used to denote a variable whose value may be changed by multiple threads.

Purpose of volatile:

• Ensures that reading and writing the variable occurs directly from main memory, not from the processor cache.
• Provides visibility of changes to the variable across threads — if one thread changes the value, others will immediately see the update.

Important:

• volatile does not guarantee atomicity of complex operations (e.g., increment), only visibility.
• Used for flags and simple states where synchronization blocks are not needed.

Example:

class Example {
    private volatile boolean flag = false;

    public void setFlag() {
        flag = true; // change will be visible to other threads immediately
    }

    public void checkFlag() {
        if (flag) {
            // will execute as soon as flag becomes true
        }
    }
}