手寫阻塞隊列（Condition實現）

自己實現阻塞隊列的話可以采用Object下的wait和notify方法，也可以使用Lock鎖提供的Condition來實現，本文就是自己手擼的一個簡單的阻塞隊列，部分借鑒了JDK的源碼。Ps：最近看面經的時候發現字節跳動的面試官特別喜歡讓面試者手寫阻塞隊列，希望本文能對大家有幫助。個人手擼如有錯誤還請批評指正。

public class AxinBlockQueue {
    //隊列容器
    private List<Integer> container = new ArrayList<>();
    private volatile int size;
    private volatile int capacity;
    private Lock lock = new ReentrantLock();
    //Condition
    private final Condition isNull = lock.newCondition();
    private final Condition isFull = lock.newCondition();

    AxinBlockQueue(int cap) {
        this.capacity = cap;
    }

    /**
     * 添加方法
     *
     * @param data
     */
    public void add(int data) {
        try {
            lock.lock();
            try {
                while (size >= capacity) {
                    System.out.println("阻塞隊列滿了");
                    isFull.await();
                }
            } catch (InterruptedException e) {
                isFull.signal();
                e.printStackTrace();
            }
            ++size;
            container.add(data);
            isNull.signal();
        } finally {
            lock.unlock();
        }
    }

    /**
     * 取出元素
     *
     * @return
     */
    public int take() {
        try {

            lock.lock();
            try {
                while (size == 0) {
                    System.out.println("阻塞隊列空了");
                    isNull.await();
                }
            } catch (InterruptedException e) {
                isNull.signal();
                e.printStackTrace();
            }
            --size;
            int res = container.get(0);
            container.remove(0);
            isFull.signal();
            return res;
        } finally {
            lock.unlock();
        }
    }
}

下面是測試部分：更改生產者和消費者的延時可以看到阻塞隊列滿了和空了的效果。

public static void main(String[] args) {
    AxinBlockQueue queue = new AxinBlockQueue(5);
    Thread t1 = new Thread(() -> {
        for (int i = 0; i < 100; i++) {
            queue.add(i);
            System.out.println("塞入" + i);
            try {
                Thread.sleep(500);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    });
    Thread t2 = new Thread(() -> {
        for (; ; ) {
            System.out.println("消費"+queue.take());
            try {
                Thread.sleep(800);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    });
    t1.start();
    t2.start();
}