Concurrency is a fundamental concept in software development that allows programs to execute multiple tasks simultaneously. This tutorial will guide you through the basics of concurrency in practice, covering various aspects such as threads, locks, and synchronization.

Introduction to Concurrency

Concurrency is the ability of a system to execute multiple tasks at the same time. It is crucial for building responsive and efficient applications, especially in today's multi-core processors and distributed systems.

Key Concepts

  • Thread: A thread is a sequence of instructions that can be executed independently of other threads.
  • Lock: A lock is a synchronization mechanism that ensures that only one thread can access a shared resource at a time.
  • Synchronization: Synchronization is the process of coordinating the execution of multiple threads to avoid conflicts and ensure data consistency.

Understanding Threads

Threads are the building blocks of concurrency. They allow multiple tasks to run concurrently within a single process.

Creating a Thread

To create a thread in most programming languages, you typically use a thread library or framework. Here's an example in Java:

Thread thread = new Thread(new Runnable() {
    @Override
    public void run() {
        // Task to be executed by the thread
    }
});
thread.start();

Synchronization Mechanisms

Synchronization mechanisms are used to control access to shared resources and ensure data consistency.

Locks

Locks are a common synchronization mechanism that provides mutual exclusion. They ensure that only one thread can access a critical section of code at a time.

Lock lock = new ReentrantLock();
lock.lock();
try {
    // Critical section
} finally {
    lock.unlock();
}

Thread Communication

Thread communication allows threads to interact with each other, enabling them to coordinate their actions.

Wait/Notify/NotifyAll

The wait(), notify(), and notifyAll() methods are used for thread communication. They allow one thread to wait for another thread to signal or notify it.

synchronized (object) {
    object.wait();
    object.notify();
    object.notifyAll();
}

Best Practices

When working with concurrency, it's important to follow best practices to ensure thread safety and avoid common pitfalls.

  • Minimize shared state: Reduce the amount of shared data between threads to minimize the chances of conflicts.
  • Use thread-safe data structures: Utilize thread-safe data structures provided by the language or framework to simplify synchronization.
  • Avoid busy waiting: Busy waiting consumes CPU resources and can lead to performance degradation.

Learn More

For a deeper understanding of concurrency, we recommend exploring the following resources:

Concurrency Diagram