1、阻塞队列和非阻塞队列
阻塞队列与非阻塞队列的区别在于，当队列是空的时，从队列中获取元素的操作将会被阻塞，或者当队列是满时，往队列里添加元素的操作会被阻塞。试图从空的阻塞队列中获取元素的线程将会被阻塞，直到其他的线程往空的队列插入新的元素。同样，试图往已满的阻塞队列中添加新元素的线程同样也会被阻塞，直到其他的线程使队列重新变得空闲起来，如从队列中移除一个或者多个元素，或者完全清空队列。
put和take属于阻塞方法；offer和pull属于非阻塞方法，可以不阻塞，也可以指定timeout操作时限。
2、常用队列
常用队列有LinkedBlockingQueue、ArrayBlockingQueue、PriorityBlockingQueue和ConcurrentLinkedQueue等。
LinkedBlockingQueue能够更高效地处理并发数据，因为其对于生产者端和消费者端分别采用了独立的锁(ReentrantLock)来控制数据同步，这也意味着在高并发的情况下生产者和消费者可以并行地操作队列中的数据，以此来提高整个队列的并发性能。LinkedBlockingQueue是基于链表实现，故在生产和消费时会频繁创建和销毁对象，对GC有一定影响。
ArrayBlockingQueue是基于数组实现的，没有实现锁分离。
PriorityBlockingQueue是一个支持线程优先级排序的无界队列，默认自然序进行排序，也可以自定义实现compareTo()方法来指定元素排序规则，不能保证同优先级元素的顺序。
ConcurrentLinkedQueue是非阻塞队列，其入队和出队操作均利用CAS更新，这样允许多个线程并发执行，并且不会因为加锁而阻塞线程，使得并发性能更好。
3、阻塞队列核心方法
public interface BlockingQueue<E> extends Queue<E> {
//将给定元素设置到队列中，如果设置成功返回true, 否则返回false。如果是往限定了长度的队列中设置值，推荐使用offer()方法。
boolean add(E e);
//将给定的元素设置到队列中，如果设置成功返回true, 否则返回false. e的值不能为空，否则抛出空指针异常。
boolean offer(E e);
//将元素设置到队列中，如果队列中没有多余的空间，该方法会一直阻塞，直到队列中有多余的空间。
void put(E e) throws InterruptedException;
//将给定元素在给定的时间内设置到队列中，如果设置成功返回true, 否则返回false.
boolean offer(E e, long timeout, TimeUnit unit)
throws InterruptedException;
//从队列中获取值，如果队列中没有值，线程会一直阻塞，直到队列中有值，并且该方法取得了该值。
E take() throws InterruptedException;
//在给定的时间里，从队列中获取值，时间到了直接调用普通的poll方法，为null则直接返回null。
E poll(long timeout, TimeUnit unit)
throws InterruptedException;
//获取队列中剩余的空间。
int remainingCapacity();
//从队列中移除指定的值。
boolean remove(Object o);
//判断队列中是否拥有该值。
public boolean contains(Object o);
//将队列中值，全部移除，并发设置到给定的集合中。
int drainTo(Collection<? super E> c);
//指定最多数量限制将队列中值，全部移除，并发设置到给定的集合中。
int drainTo(Collection<? super E> c, int maxElements);
}LinkedBlockingQueue的核心方法（take、put、offer、poll、contains）实现：
/** Lock held by take, poll, etc */
private final ReentrantLock takeLock = new ReentrantLock();
/** Wait queue for waiting takes */
private final Condition notEmpty = takeLock.newCondition();
/** Lock held by put, offer, etc */
private final ReentrantLock putLock = new ReentrantLock();
/** Wait queue for waiting puts */
private final Condition notFull = putLock.newCondition();
public E takeFirst() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lock();
try {
E x;
while ( (x = unlinkFirst()) == null)
notEmpty.await();
return x;
} finally {
lock.unlock();
}
}
public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException();
// Note: convention in all put/take/etc is to preset local var
// holding count negative to indicate failure unless set.
int c = -1;
Node<E> node = new Node(e);
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
/*
* Note that count is used in wait guard even though it is
* not protected by lock. This works because count can
* only decrease at this point (all other puts are shut
* out by lock), and we (or some other waiting put) are
* signalled if it ever changes from capacity. Similarly
* for all other uses of count in other wait guards.
*/
while (count.get() == capacity) {
notFull.await();
}
enqueue(node);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
}
public boolean offer(E e) {
if (e == null) throw new NullPointerException();
final AtomicInteger count = this.count;
if (count.get() == capacity)
return false;
int c = -1;
Node<E> node = new Node(e);
final ReentrantLock putLock = this.putLock;
putLock.lock();
try {
if (count.get() < capacity) {
enqueue(node);
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
}
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
return c >= 0;
}
public boolean offer(E e, long timeout, TimeUnit unit)
throws InterruptedException {
if (e == null) throw new NullPointerException();
long nanos = unit.toNanos(timeout);
int c = -1;
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
while (count.get() == capacity) {
if (nanos <= 0)
return false;
nanos = notFull.awaitNanos(nanos);
}
enqueue(new Node<E>(e));
c = count.getAndIncrement();
if (c + 1 < capacity)
notFull.signal();
} finally {
putLock.unlock();
}
if (c == 0)
signalNotEmpty();
return true;
}
public E pollFirst(long timeout, TimeUnit unit)
throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
E x;
while ( (x = unlinkFirst()) == null) {
if (nanos <= 0)
return null;
nanos = notEmpty.awaitNanos(nanos);
}
return x;
} finally {
lock.unlock();
}
}
public boolean contains(Object o) {
if (o == null) return false;
fullyLock();
try {
for (Node<E> p = head.next; p != null; p = p.next)
if (o.equals(p.item))
return true;
return false;
} finally {
fullyUnlock();
}
}参考资料：