java-concurrency-guidelines

To choose between synchronized and ReentrantLock for Java multithreading, apply the decision checklist based on workload. ReentrantLock is selected for advanced features like interruptible lock acquisition, whereas synchronized is preferred for simple, uncontended locking.

The Java memory model defines how threads interact with memory, and volatile ensures memory visibility by establishing happens-before relationships. This prevents threads from reading stale, cached values from CPU registers or local caches.

To review multithreaded code for thread safety, apply the structured guidelines to verify correct synchronization primitives, memory visibility, and ordering. This enforces core rules for stable data sharing and validates lock-free or lock-based patterns.

Use ReadWriteLock instead of ReentrantLock in Java concurrency when your workload involves many concurrent read operations and few writes. This locking strategy allows multiple threads to read simultaneously while blocking writes.

Volatile does not guarantee thread safety for compound actions in Java. It only ensures memory visibility and ordering for single read or write operations, requiring lock-free patterns or synchronized blocks for atomic compound actions.