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Locks

Use explicit locks for fine-grained concurrency control.

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Locks

Lock Types

Type Description
synchronized Intrinsic lock (JVM)
ReentrantLock Explicit, flexible
ReadWriteLock Multiple readers, one writer
StampedLock Optimistic + pessimistic

ReentrantLock

private final ReentrantLock lock = new ReentrantLock();

public void safeMethod() {
    lock.lock();
    try {
        // critical section
    } finally {
        lock.unlock();
    }
}

Key Points

  • Understanding Locks is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Locking Strategies

Lock Types

  • Mutex: Mutual exclusion
  • Read-Write: Multiple readers, single writer
  • Reentrant: Same thread reacquire
  • Stamped: Optimistic + pessimistic

Best Practices

  • Always release in finally
  • Use tryLock for timeouts
  • Prefer read-write locks
  • Minimize lock scope

Deadlock Prevention

  • Consistent lock ordering
  • Lock timeouts
  • Avoid nested locks
  • Use lock-free algorithms

Key Points

  • Understanding Locks is essential for production systems
  • Always consider scalability and maintainability
  • Test thoroughly before deploying to production
  • Monitor performance and set up alerting

Common Patterns

  1. Validation: Always validate input at the boundary
  2. Error Handling: Use structured error responses
  3. Logging: Log key events for debugging
  4. Testing: Unit, integration, and load tests
  5. Documentation: Keep docs updated with code changes

Practice Problems

0/3solved
Implement Locks

Design and implement a solution for Locks in a backend system. Consider scalability, error handling, and production readiness.

Solution
// Locks implementation
// Key aspects: validation, error handling, logging, testing

public class Locks {
    // Production-ready implementation
}
Locks Edge Cases

Identify and handle edge cases for Locks. What happens under high load, with invalid input, or during failures?

Solution
// Edge case handling:
// 1. Null/empty input -> validation
// 2. High load -> rate limiting, queuing
// 3. Failures -> retries, circuit breaker
// 4. Concurrent access -> locks, idempotency
Locks Testing Strategy

Write a testing strategy for Locks. Include unit tests, integration tests, and performance tests.

Solution
// Test plan:
// - Unit: 80% coverage target
// - Integration: API contracts
// - Performance: latency, throughput
// - Chaos: failure injection

Quiz

1. ReentrantLock is?

Question 1 options

2. ReadWriteLock allows?

Question 2 options

3. What is the primary purpose of Locks?

Question 3 options

4. What is a common mistake when implementing Locks?

Question 4 options

Flashcards

Question

ReentrantLock vs synchronized?

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Answer

ReentrantLock: explicit, more features

Question

ReadWriteLock?

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Answer

Multiple readers, one writer

Question

What is Locks?

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Answer

Locks is a key concept in backend development.

Question

When to use Locks?

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Answer

Use Locks when building production systems that require reliability, scalability, and maintainability.

Question

Locks best practices

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Answer

Follow SOLID principles, write clean code, test thoroughly, document decisions, and monitor in production.

Revision Notes

Key Takeaways

  • 1.synchronized: simple, intrinsic lock
  • 2.ReentrantLock: explicit, more flexible
  • 3.ReadWriteLock: multiple readers, one writer
  • 4.Always unlock in finally block

Interview Tips

  • •Use locks correctly
  • •Know lock types

Cheat Sheet

Locks

  • synchronized: simple, intrinsic
  • ReentrantLock: explicit, flexible
  • ReadWriteLock: readers + 1 writer
  • Always unlock in finally