What are the differences between synchronized and volatile in Java?

What are the differences between synchronized and volatile in Java?

Synchronized is a keyword used to control access to a block of code or an object, ensuring that only one thread can execute it at a time. Volatile, on the other hand, is used to indicate that a variable's value will be modified by different threads, ensuring visibility of changes across threads.

Can you explain how synchronized works in detail?

Sure! When a method or block is marked as synchronized, a thread must acquire the lock for that object before executing it. This prevents other threads from entering any synchronized block on the same object until the lock is released.

What about volatile? How does it ensure visibility?

Volatile ensures visibility by forcing the JVM to read the variable from main memory instead of from the thread's local cache. This means that any changes made to a volatile variable are immediately visible to all threads.

When should I use synchronized over volatile?

Use synchronized when you need to control access to a block of code or when you need atomicity. Use volatile when you only need to ensure visibility of changes to a variable without needing to lock the entire block of code.