12_读锁和写锁

• 读锁又叫共享锁，写锁又叫排他锁/独占锁。
• 读锁和写锁都会发生死锁
• 读锁和写锁是为了解决多线程读写问题的一种锁机制.

ReadWriteLock

• 读写锁是一种读写分离锁，读读共享，读写互斥，写写互斥。
• 读写锁的实现类ReentrantReadWriteLock，内部有两个锁，一个读锁，一个写锁。
• ReentrantReadWriteLock的使用示例:

public class ReadWriteLockDemo {
    private int count = 0;
    private ReentrantReadWriteLock lock = new ReentrantReadWriteLock();

    public void increment() {
        lock.writeLock().lock();
        try {
            count++;
        } finally {
            lock.writeLock().unlock();
        }
    }

    public int getCount() {
        lock.readLock().lock();
        try {
            return count;
        } finally {
            lock.readLock().unlock();
        }
    }

    public static void main(String[] args) throws InterruptedException {
        ReadWriteLockDemo counter = new ReadWriteLockDemo();

        Thread thread1 = new Thread(() -> {
            for (int i = 0; i < 1000; i++) {
                counter.increment();
            }
        });

        Thread thread2 = new Thread(() -> {
            for (int i = 0; i < 1000; i++) {
                counter.increment();
            }
        });

        thread1.start();
        thread2.start();
        thread1.join();
        thread2.join();

        System.out.println("Final count: " + counter.getCount());
    }
}