What are some examples of semaphore implementations in programming?

What are some examples of semaphore implementations in programming?

Semaphore is a synchronization mechanism used to control access to a common resource in concurrent programming. Examples include using semaphores in multi-threaded applications to manage access to shared data.

Can you give me a specific example in Python?

Sure! In Python, you can use the threading module. Here's a simple example:

import threading

# Create a semaphore with a limit of 2
semaphore = threading.Semaphore(2)

def access_resource(thread_id):
    print(f'Thread {thread_id} is trying to access the resource.')
    semaphore.acquire()
    print(f'Thread {thread_id} has accessed the resource.')
    # Simulate resource access
    semaphore.release()
    print(f'Thread {thread_id} has released the resource.')

# Create multiple threads
threads = [threading.Thread(target=access_resource, args=(i,)) for i in range(5)]

for thread in threads:
    thread.start()

for thread in threads:
    thread.join()

What about semaphore usage in Java?

In Java, you can use the Semaphore class from the java.util.concurrent package. Here's a quick example:

import java.util.concurrent.Semaphore;

public class SemaphoreExample {
    private static final Semaphore semaphore = new Semaphore(2);

    public static void accessResource(int threadId) throws InterruptedException {
        System.out.println("Thread " + threadId + " is trying to access the resource.");
        semaphore.acquire();
        System.out.println("Thread " + threadId + " has accessed the resource.");
        // Simulate resource access
        semaphore.release();
        System.out.println("Thread " + threadId + " has released the resource.");
    }

    public static void main(String[] args) throws InterruptedException {
        for (int i = 0; i < 5; i++) {
            final int threadId = i;
            new Thread(() -> {
                try {
                    accessResource(threadId);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }).start();
        }
    }
}