实例解析：Java多线程并发控制疑问

原创一时失言乱红尘 2024-10-07 12:48 38阅读 0赞

在Java多线程编程中，经常会遇到一些并发控制的问题。这里举个例子，帮助你理解：

1. **锁（Synchronized）**：
   当一个方法需要保护其内部数据不被其他线程修改时，可以使用synchronized关键字来实现同步。

```java
public class Counter {
    private int count = 0;

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

public synchronized int decrement() {
        if (count > 0) {
            count--;
            return count;
        } else {
            throw new IllegalArgumentException("Counter is already zero");
        }
    }
}
```
2. **条件变量（Condition）**：
   Java并发API中提供了`java.util.concurrent.locks.Condition`接口，用于实现线程间的等待和唤醒。

```java
public class PrintQueue {
    private final Object lock = new Object();
    private final Condition empty = new Condition(lock);
    private int count = 0;

public void enqueue() {
        synchronized (lock) {
            if (count < 5) { // queue is not full
                count++;
                empty.signalAll(); // wake up all waiting threads
                return;
            }
        }
        System.out.println("Queue is full, cannot enqueue.");
    }

public void dequeue() throws InterruptedException {
        synchronized (lock) {
            while (count == 0) { // queue is empty
                empty.await(); // wait for the queue to become non-empty
            }
            count--;
            System.out.println("Dequeue operation completed. Remaining in queue: " + count);
            empty.signalAll(); // wake up all waiting threads
        }
    }
}
```
以上实例解析了Java多线程编程中如何使用锁和条件变量来实现并发控制。