二十二、并发编程之使用Condition实现一个先入先出的有界队列

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//先入先出队列
public class MyQueue<E> {
	private Object[] obj;//数组（队列）
	private int addIndex;//添加角标
	private int removeIndex;//移除脚标
	private int queueSize;//队列长度
	private Lock lock = new ReentrantLock();
	Condition addCondition = lock.newCondition();
	Condition removeCondition = lock.newCondition();
	
	//在构造器里设置队列长度
	public MyQueue(int count) {
		obj = new Object[count];
	}

	//添加
	public void add(E e) {
		lock.lock();//加锁
		while (queueSize == obj.length) {//假如队列长度等于数组长度，说明队列已满
			try {
				System.out.println("队列已满："+Arrays.toString(obj));
				addCondition.await();//添加线程等待
			} catch (InterruptedException e1) {
				e1.printStackTrace();
			}
		}
		obj[addIndex] = e;//将元素e添加进数据
		if (++addIndex == obj.length) {//如果添加脚标加1等于数组的长度，将添加脚标设置为0
			addIndex = 0;
		}
		queueSize++;//队列长度加1
		removeCondition.signal();//唤醒移除线程
		System.out.println("新增："+Arrays.toString(obj));
		lock.unlock();//释放锁
	}

	//移除
	public void remove() {
		lock.lock();//加锁
		while (queueSize == 0) {//如果队列为0，表示队列空的
			try {
				System.out.println("队列为空："+Arrays.toString(obj));
				removeCondition.await();//移除线程等待
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		obj[removeIndex] = null;//将第removeIndex元素设置为null

		if (++removeIndex == obj.length) {//如果removeIndex加1等于数组长度，将removeIndex设置为0
			removeIndex = 0;
		}
		queueSize--;//队列长度减1
		addCondition.signal();//唤醒添加线程
		System.out.println("删除："+Arrays.toString(obj));
		lock.unlock();//释放锁
	}

	public static void main(String[] args) {
		MyQueue q = new MyQueue(4);
		new Thread(new Runnable() {
			@Override
			public void run() {
				for(int i = 0;i<100;i++) {
					q.add(i);
					try {
						Thread.sleep(1000);
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
		}).start();

		new Thread(new Runnable() {
			@Override
			public void run() {
				for(int i = 0;i<100;i++) {
					q.remove();
					try {
						Thread.sleep(3000);
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
		}).start();
	}
}