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

    public class ProductQueue<T> {

    private T[]       items;
    private Lock      lock         = new ReentrantLock();
    final static int  DEAFULT_SIZE = 10;

    //滿佇列條件
    private Condition notFull      = lock.newCondition();

    //空佇列條件
    private Condition notEmpty     = lock.newCondition();

    private int       head, tail, count;

    @SuppressWarnings("unchecked")
    public ProductQueue(int size) {
        items = (T[]) new Object[size];
    }

    public ProductQueue() {
        this(DEAFULT_SIZE);
    }

    /**
     * 生產產品
     * 
     * @param t
     * @throws InterruptedException
     */
    public void put(T t) throws InterruptedException {
        lock.lock();//獲取獨佔鎖
        try {
            Thread.sleep(2 * 1000);
            while (count == getCapacity()) {//佇列已滿，掛起當前 執行緒，將當前執行緒加入條件鎖佇列中，直到收到佇列不為滿的訊號，從佇列中按照FIFO喚醒一個執行緒
                notFull.await(); //釋放獨佔鎖 ，讓其他執行緒（消費者執行緒）獲取，然後掛起當前執行緒，一旦後續條件滿足，再次獲取鎖
            }
            items[tail] = t;
            if (++tail == getCapacity()) {
                tail = 0;
            }
            ++count;
            notEmpty.signalAll();//佇列已不為空，可以喚醒消費者 消費產品
        } finally {
            lock.unlock();
        }

    }

    /**
     * 消費產品
     * 
     * @return
     * @throws InterruptedException
     */
    public T get() throws InterruptedException {
        lock.lock();
        try {
            while (count == 0) {//佇列已空，掛起空佇列鎖條件 執行緒，直到收到不為空的訊號，被喚醒
                notEmpty.await();
            }
            T ret = items[head];
            items[head] = null;
            if (++head == getCapacity()) {
                head = 0;
            }
            --count;
            notFull.signalAll();//佇列已不為滿，可以喚醒生產者  生產產品
            return ret;

        } finally {
            lock.unlock();
        }
    }

    /**
     * 產品佇列容量
     * 
     * @return
     */
    public int getCapacity() {
        return items.length;
    }

    /**
     * 當前產品數量
     * 
     * @return
     */
    public int size() {
        lock.lock();
        try {
            return count;
        } finally {
            lock.unlock();
        }
    }

}

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