Volatile vs Synchronized in Java: Key Differences

1. The volatile keyword is used to ensure the visibility of variables and prevent instruction reordering, but it does not guarantee atomicity. When a variable is declared volatile, each operation on that variable will directly read from the main memory instead of the thread’s working memory. This ensures that operations on the variable are visible to different threads.
2. The ‘synchronized’ keyword is used to ensure the atomicity and visibility of code blocks or methods, preventing data inconsistency issues caused by concurrent access. When a thread obtains the lock of an object, all other threads attempting to obtain the lock will be blocked until the locking thread releases it.

In summary, volatile is used to ensure visibility and prevent reordering of variables, while synchronized is used to ensure atomicity and visibility of code blocks or methods. Volatile is used for simple variable operations, while synchronized is used for synchronizing complex code blocks or methods.