Java多线程并发问题：共享资源的处理

原创迷南。 2024-09-29 22:51 164阅读 0赞

在Java多线程并发中，共享资源的处理是一项重要的任务。以下是一些主要的处理方式：

1. **同步**：使用synchronized关键字或者Lock接口来保证同一时间只有一个线程访问共享资源。

```java
public class Counter {
    private int count;

synchronized public void increment() {
        count++;
    }

synchronized public int decrement() {
        if (count > 0) {
            count--;
            return count;
        } else {
            throw new IllegalStateException("Counter is already at zero.");
        }
    }

public int getCount() {
        synchronized (this) {
            return count;
        }
    }
}
```

2. **使用Lock接口**：相比synchronized，Lock提供了更多的灵活性。

```java
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Counter {
    private int count;
    private Lock lock = new ReentrantLock();

public synchronized void increment() {
        count++;
        lock.lock();
        try {
            // update count here
            System.out.println("Incremented: " + count);
        } finally {
            lock.unlock();
        }
    }

public synchronized int decrement() {
        if (count > 0) {
            count--;
            lock.lock();
            try {
                // update count here
                System.out.println("Decremented: " + count);
            } finally {
                lock.unlock();
            }
            return count;
        } else {
            throw new IllegalStateException("Counter is already at zero.");
        }
    }

public int getCount() {
        synchronized (this) {
            return count;
        }
    }
}
```

3. **使用原子变量**：Atomic类提供了对共享资源进行原子操作的方法。

```java
import java.util.concurrent.atomic.AtomicInteger;

public class Counter {
    private AtomicInteger count;

public AtomicInteger getCount() {
        return count;
    }

// 使用AtomicInteger进行原子操作
    public void increment() {
        count.incrementAndGet();
        System.out.println("Incremented: " + count.get());
    }

public void decrement() {
        if (count.get() > 0) {
            count.decrementAndGet();
            System.out.println("Decremented: " + count.get());
        } else {
            throw new IllegalStateException("Counter is already at zero.");
        }
    }
}
```

在实际应用中，根据具体需求和资源特性选择合适的处理方式。