What Are Volatile Variables

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It indicates that these variables can be modified asynchronously.

In Java, the volatile keyword is used to indicate that a variable’s value may be changed by multiple threads simultaneously. It ensures that any thread that reads the variable sees the most recent modification made by any other thread. When a variable is declared as volatile, it prevents the compiler and the runtime environment from reordering code to optimize performance, and it also ensures that changes to the variable are immediately visible to other threads.

Key points about volatile variables in Java:

  1. Visibility: Changes to a volatile variable are immediately visible to other threads.
  2. Atomicity: The individual read and write operations on a volatile variable are atomic. However, compound actions like check-then-act are not atomic and may require additional synchronization.
  3. No Caching: The value of a volatile variable is not cached by individual threads. Instead, each thread reads and writes directly from and to the main memory.
  4. Use Cases: volatile is typically used in scenarios where a variable is shared among multiple threads, and the developer wants to ensure that changes made by one thread are immediately visible to others. It is not a substitute for proper synchronization mechanisms in more complex scenarios.

Here’s an example of using the volatile keyword:

java
public class SharedResource {
private volatile boolean flag = false;public void setFlagTrue() {
flag = true;
}

public boolean isFlag() {
return flag;
}
}

In this example, the flag variable is declared as volatile to ensure that changes made by one thread to the flag variable are immediately visible to other threads.

Keep in mind that while volatile provides some level of thread safety for simple use cases, for more complex operations and compound actions, you may need to use additional synchronization mechanisms such as synchronized blocks or Locks.