Avoiding race conditions and deadlocks

Avoiding race conditions and deadlocks is essential for developing robust and efficient multithreaded applications in Java. Below are best practices categorized for both issues:

Race Conditions

1. Synchronize Access to Shared Mutable State
   Use synchronization mechanisms such as synchronized blocks or methods, or utilize java.util.concurrent locks (e.g., ReentrantLock, ReadWriteLock) to ensure that only one thread can access a shared mutable resource at any time.

2. Use Thread-Safe Data Structures
   Prefer using thread-safe collections such as ConcurrentHashMap, CopyOnWriteArrayList, and others from the java.util.concurrent package. These manage synchronization internally, reducing the chances of race conditions.

3. Avoid Mutable Shared State
   Design classes and data to be immutable wherever feasible. Immutable objects are inherently thread-safe and eliminate the need for synchronization.

4. Minimize the Scope of Synchronized Blocks
   Keep synchronized sections as short and focused as possible to reduce contention and improve overall concurrency and performance.

Deadlocks

1. Avoid Nested Locks or Always Acquire Locks in a Consistent Order
   If you need multiple locks, always acquire them in a consistent global order across all threads to avoid circular waits, which lead to deadlocks.

2. Use Timed Lock Acquisition
   Instead of waiting indefinitely for a lock, use locking mechanisms with timeout capabilities. This allows the thread to back out gracefully and avoid deadlock if the lock is not acquired within the time limit.

3. Avoid Holding Locks During Blocking Operations
   Do not perform operations that may block (like I/O or waiting on conditions) while holding a lock. Always release locks before entering potentially blocking operations.

4. Use Higher-Level Concurrency Utilities
   Use abstractions like ExecutorService, Semaphore, CountDownLatch, CyclicBarrier, and Phaser provided by java.util.concurrent. These utilities handle low-level synchronization more safely and reduce the chances of deadlocks.

General Best Practices

• Use Thread-Safe Libraries: Ensure any third-party libraries or frameworks used in a multithreaded context are thread-safe.

• Thorough Testing: Write comprehensive tests, including multithreaded scenarios, to detect concurrency bugs during development.

• Code Review: Conduct peer code reviews to identify and address potential concurrency issues early in the development lifecycle.