What behavior does the use of the volatile keyword ensure in multithreaded programming in Java?

The volatile keyword in Java guarantees that reads and writes to a variable are directly from main memory, not from the CPU cache. This provides:

• Visibility of changes between threads: when one thread updates a volatile variable, other threads immediately see the change.
• Prevents compiler and processor optimizations that could reorder operations involving the volatile variable.

However, volatile does not guarantee atomicity of operations, so for complex operations (like increment), additional synchronization mechanisms are needed.

Example:

volatile boolean flag = false;

// Thread 1
flag = true;

// Thread 2
if (flag) {
    // will definitely see the updated value
}