多线程并发控制工具Semaphore的使用详解

import java.util.concurrent.Semaphore;

public class SemaphoreTest {

    public static void main(String[] args) {
        final DatabaseConnectionPool pool = new DatabaseConnectionPool(3);

        // 创建多个线程以模拟数据库连接
        Thread thread1 = new Thread(() -> pool.connect("Thread 1"));
        Thread thread2 = new Thread(() -> pool.connect("Thread 2"));
        Thread thread3 = new Thread(() -> pool.connect("Thread 3"));
        Thread thread4 = new Thread(() -> pool.connect("Thread 4"));
        Thread thread5 = new Thread(() -> pool.connect("Thread 5"));


        thread1.start();
        thread2.start();
        thread3.start();
        thread4.start();
        thread5.start();

    }
}


class DatabaseConnectionPool{
    private final Semaphore semaphore;

    DatabaseConnectionPool(int maxConnections) {
        this.semaphore = new Semaphore(maxConnections,true);
    }

    public void connect(String threadName) {
        try {
            System.out.println(threadName + " is trying to connect.");
            // 获取许可
            semaphore.acquire();
            System.out.println(threadName + " has connected to the database.");
            // 模拟使用连接
            Thread.sleep(5000); // 模拟数据库操作
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
        } finally {
            // 释放许可
            System.out.println(threadName + " is releasing the connection.");
            semaphore.release();
        }
    }
}

public DatabaseConnectionPool(int maxConnections) {
    this.semaphore = new Semaphore(maxConnections);
}

semaphore.acquire();

semaphore.release();