concurrent包的数据结构

concurrent包的数据结构：阻塞的结构都是用lock加锁(lock会休眠锁)，非阻塞是用CAS直接for循环加入。

• 结构简介

名称	功能	组成
原子量
AtomicBoolean		Unsafe+==volatile int value==
AtomicInteger		Unsafe+==volatile int value==
AtomicIntegerArray		Unsafe+==final int[] array==
AtomicLong		Unsafe+==volatile long value==
AtomicLongArray		Unsafe+==final int[] array==

名称	功能	组成
阻塞队列		==继承:BlockingQueue接口==
ArrayBlockingQueue		数组+lock
LinkedBlockingQueue		链表+lock
PriorityBlockingQueue**(优先级队列)**	自定义哪个队列先出	数组+lock
DelayQueue (时间队列)	队列中每个元素都有个过期时间，并且队列是个优先级队列，当从队列获取元素时候，只有过期元素才会出队列	PriorityQueue(优先级队列)+lock
SynchronousQueue	一个不存储元素的阻塞队列
阻塞队列(双端)		==继承:BlockingDeque接口==
LinkedBlockingDeque(阻塞双端链表队列)		链表+lock
非阻塞队列
ConcurrentLinkedDeque(非阻塞双端队列)	添加线程不会休眠，一直for循环添加直到成功	链表(UnSafe)
ConcurrentLinkedQueue(非阻塞队列)	添加线程不会休眠，一直for循环添加直到成功	链表(UnSafe)
其它容器
ConcurrentHashMap(非阻塞的hasMap)

DelayQueue：延时队列。

• 队列中每个元素都有个过期时间，并且队列是个优先级队列，当从队列获取元素时候，只有过期元素才会出队列

• 出队源码:会比较时间

public E poll() {
    final ReentrantLock lock = this.lock;
    lock.lock();
    try {
        E first = q.peek();
        if (first == null || first.getDelay(TimeUnit.NANOSECONDS) > 0)
            return null;
        else
            return q.poll();
    } finally {
        lock.unlock();
    }
}

• 添加类:需要实现Delayed

'实现类'

public class TestDelay implements Delayed {

	@Override
	public int compareTo(Delayed o) {
		return 0;
	}

	@Override
	public long getDelay(TimeUnit unit) {
		return 0;
	}

}

'添加'

	BlockingQueue bq = new DelayQueue<>();
	bq.add(new TestDelay());
	

PriorityBlockingQueue：优先级队列

• 核心源码

'弹出'
public E poll() {
    final ReentrantLock lock = this.lock;
    lock.lock();
    try {
        return dequeue();
    } finally {
        lock.unlock();
    }
}

'调用dequeue()'
private E dequeue() {
    int n = size - 1;
    if (n < 0)
        return null;
    else {
        Object[] array = queue;
        E result = (E) array[0];
        E x = (E) array[n];
        array[n] = null;
        Comparator<? super E> cmp = comparator;
        if (cmp == null)
            siftDownComparable(0, x, array, n);
        else
            siftDownUsingComparator(0, x, array, n, cmp);
        size = n;
        return result;
    }
}

'调用siftDownUsingComparator()'
private static <T> void siftDownUsingComparator(int k, T x, Object[] array,
                                                int n,
                                                Comparator<? super T> cmp) {
    if (n > 0) {
        int half = n >>> 1;
        while (k < half) {
            int child = (k << 1) + 1;
            Object c = array[child];
            int right = child + 1;
            if (right < n && cmp.compare((T) c, (T) array[right]) > 0)
                c = array[child = right];
            if (cmp.compare(x, (T) c) <= 0)
                break;
            array[k] = c;
            k = child;
        }
        array[k] = x;
    }
}

• 使用：implements Comparator

'implements Comparator'
public class TestPrority implements Comparator {

	@Override
	public int compare(Object o1, Object o2) {
		return 0;
	}

}

'添加'
BlockingQueue bq = new PriorityBlockingQueue<>();
bq.add(new TestPrority());

来源：oschina

链接：https://my.oschina.net/u/2246410/blog/1800728