深入理解ReadWriteLock读写锁：提升多线程并发性能的关键

import java.util.concurrent.locks.ReentrantReadWriteLock;

class SharedResource {
    private int count = 0;
    private final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

    public int getCount() {
        lock.readLock().lock(); // 获取读锁
        try {
            return count;
        } finally {
            lock.readLock().unlock(); // 释放读锁
        }
    }

    public void increment() {
        lock.writeLock().lock(); // 获取写锁
        try {
            count++;
        } finally {
            lock.writeLock().unlock(); // 释放写锁
        }
    }
}

public class Main {
    public static void main(String[] args) {
        SharedResource resource = new SharedResource();

        Runnable reader = () -> {
            for (int i = 0; i < 5; i++) {
                int value = resource.getCount();
                System.out.println("Reader: " + Thread.currentThread().getId() + " - Value: " + value);
            }
        };

        Runnable writer = () -> {
            for (int i = 0; i < 5; i++) {
                resource.increment();
                System.out.println("Writer: " + Thread.currentThread().getId() + " - Incremented");
            }
        };

        // 创建多个读线程和写线程
        Thread[] readers = new Thread[3];
        Thread[] writers = new Thread[2];

        for (int i = 0; i < 3; i++) {
            readers[i] = new Thread(reader);
            readers[i].start();
        }

        for (int i = 0; i < 2; i++) {
            writers[i] = new Thread(writer);
            writers[i].start();
        }

        // 等待线程完成
        for (Thread readerThread : readers) {
            try {
                readerThread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

        for (Thread writerThread : writers) {
            try {
                writerThread.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}