阻塞队列和非阻塞队列
阻塞队列和非阻塞队列的区别：阻塞队列可以自己阻塞，非阻塞队列不能自己阻塞，只能使用队列wait(),notify()进行队列消息传送。而阻塞队列当队列里面没有值时，会阻塞直到有值输入。输入也一样，当队列满的时候，会阻塞，直到队列不为空。
阻塞队列不需要synchronized,或者调用wait，notify()来进行队列交互。
非阻塞队列：
queue.wait();queue.notify();是synchronized (queue)的queue对象调用的，睡眠和唤醒是线程的睡眠和唤醒，
public class feizusheQueue
{
private int queueSize = 10;
private PriorityQueue<Integer> queue = new PriorityQueue<Integer>(queueSize); public static void main(String[] args) {
feizusheQueue test = new feizusheQueue ();
Producer producer = test.new Producer();
Consumer consumer = test.new Consumer(); producer.start();
consumer.start();
} class Consumer extends Thread{ @Override
public void run() {
consume();
} private void consume() {
while(true){
synchronized (queue) {
while(queue.size() == 0){
try {
System.out.println("队列空，等待数据");
queue.wait();
} catch (InterruptedException e) {
e.printStackTrace();
queue.notify();
}
}
queue.poll(); //每次移走队首元素
queue.notify();//执行完，不马上释放锁，synchronized执行完之后释放锁。
System.out.println("从队列取走一个元素，队列剩余"+ queue.size()+"个元素");
}
}
}
} class Producer extends Thread{ @Override
public void run() {
produce();
} private void produce() {
while(true){
synchronized (queue) {
while(queue.size() == queueSize){
try {
System.out.println("队列满，等待有空余空间");
queue.wait();
} catch (InterruptedException e) {
e.printStackTrace();
queue.notify();
}
}
queue.offer(1); //每次插入一个元素
queue.notify();
System.out.println("向队列取中插入一个元素，队列剩余空间："+ (queueSize-queue.size()));
}
}
}
}
}
阻塞队列：
public class zusheQueue {
private int queueSize = 10;
private ArrayBlockingQueue<Integer> queue = new ArrayBlockingQueue<Integer>(queueSize);
public static void main(String[] args) {
zusheQueue test = new zusheQueue();
Producer producer = test.new Producer();
Consumer consumer = test.new Consumer();
producer.start();
consumer.start();
}
class Consumer extends Thread{
@Override
public void run() {
consume();
}
private void consume() {
while(true){
try {
queue.take();
System.out.println("从队列取走一个元素，队列剩余"+ queue.size()+"个元素");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
class Producer extends Thread{
@Override
public void run() {
produce();
}
private void produce() {
while(true){
try {
queue.put(1);
System.out.println("向队列取中插入一个元素，队列剩余空间："+ (queueSize-queue.size()));
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
lock.lock();当其他线程获取了这个锁，这和线程也获取不到这个锁了。condition.signal();但是外层的lock没有释放，还是走不了的。只唤醒一个消费者。
阻塞队列中的几个主要方法：
put方法用来向队尾存入元素，如果队列满，则等待；
offer方法用来向队尾存入元素，如果队列满，则等待一定的时间，当时间期限达到时，如果还没有插入成功，则返回false；否则返回true；
take方法用来从队首取元素，如果队列为空，则等待；
poll方法用来从队首取元素，如果队列空，则等待一定的时间，当时间期限达到时，如果取到，则返回null；否则返回取得的元素；
put(E e) take() offer(E e,long timeout, TimeUnit unit) poll(long timeout, TimeUnit unit)
非阻塞队列中的几个主要方法：
add(E e)：将元素e插入到队列末尾，如果插入成功，则返回true；如果插入失败（即队列已满），则会抛出异常；
remove()：移除队首元素，若移除成功，则返回true；如果移除失败（队列为空），则会抛出异常；
offer(E e)：将元素e插入到队列末尾，如果插入成功，则返回true；如果插入失败（即队列已满），则返回false；
poll()：移除并获取队首元素，若成功，则返回队首元素；否则返回null；
peek()：获取队首元素，若成功，则返回队首元素；否则返回null
对于非阻塞队列，一般情况下建议使用offer、poll和peek三个方法，不建议使用add和remove方法。因为使用offer、poll和peek三个方法可以通过返回值判断操作成功与否，而使用add和remove方法却不能达到这样的效果。注意，非阻塞队列中的方法都没有进行同步措施。
阻塞队列：
ArrayBlockingQueue：数组，在创建ArrayBlockingQueue对象时必须制定容量大小。并且可以指定公平性与非公平性，默认情况下为非公平的，即不保证等待时间最长的队列最优先能够访问队列。
LinkedBlockingQueue：链表，在创建LinkedBlockingQueue对象时如果不指定容量大小，则默认大小为Integer.MAX_VALUE。
PriorityBlockingQueue：以上2种队列都是先进先出队列，而PriorityBlockingQueue却不是，它会按照元素的优先级对元素进行排序，按照优先级顺序出队，每次出队的元素都是优先级最高的元素。注意，此阻塞队列为*阻塞队列，即容量没有上限（通过源码就可以知道，它没有容器满的信号标志），前面2种都是有界队列。
DelayQueue：基于PriorityQueue，一种延时阻塞队列，DelayQueue中的元素只有当其指定的延迟时间到了，才能够从队列中获取到该元素。DelayQueue也是一个*队列，因此往队列中插入数据的操作（生产者）永远不会被阻塞，而只有获取数据为空的操作（消费者）才会被阻塞。
public class ArrayBlockingQueue<E> extends AbstractQueue<E>
implements BlockingQueue<E>, java.io.Serializable {
final Object[] items;
int takeIndex; //下一个要取的位置
int putIndex; //下一个要放的位置
int count;
final ReentrantLock lock;
private final Condition notEmpty;
private final Condition notFull;
public ArrayBlockingQueue(int capacity, boolean fair) {
if (capacity <= 0)
throw new IllegalArgumentException();
this.items = new Object[capacity];
lock = new ReentrantLock(fair);
notEmpty = lock.newCondition();
notFull = lock.newCondition();
}
public void put(E e) throws InterruptedException {
checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == items.length)
notFull.await();
enqueue(e);
} finally {
lock.unlock();
}
}
private void enqueue(E x) {
// assert lock.getHoldCount() == 1;
// assert items[putIndex] == null;
final Object[] items = this.items;
items[putIndex] = x;
if (++putIndex == items.length)
putIndex = 0;
count++;
notEmpty.signal();
}
public E take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == 0)
notEmpty.await();
return dequeue();
} finally {
lock.unlock();
}
}
private E dequeue() {
// assert lock.getHoldCount() == 1;
// assert items[takeIndex] != null;
final Object[] items = this.items;
@SuppressWarnings("unchecked")
E x = (E) items[takeIndex];
items[takeIndex] = null;
if (++takeIndex == items.length)
takeIndex = 0;
count--;
if (itrs != null)
itrs.elementDequeued();
notFull.signal();
return x;
}
public boolean offer(E e) {
checkNotNull(e);
final ReentrantLock lock = this.lock;
lock.lock();
try {
if (count == items.length)
return false;
else {
enqueue(e);
return true;
}
} finally {
lock.unlock();
}
}
public boolean offer(E e, long timeout, TimeUnit unit)
throws InterruptedException { checkNotNull(e);
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == items.length) {
if (nanos <= 0)//时间到了就返回
return false;
nanos = notFull.awaitNanos(nanos);
}
enqueue(e);
return true;
} finally {
lock.unlock();
}
}
public E poll() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return (count == 0) ? null : dequeue();
} finally {
lock.unlock();
}
}
public E take() throws InterruptedException {
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == 0)
notEmpty.await();
return dequeue();
} finally {
lock.unlock();
}
}
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
long nanos = unit.toNanos(timeout);
final ReentrantLock lock = this.lock;
lock.lockInterruptibly();
try {
while (count == 0) {
if (nanos <= 0)//时间到了就返回
return null;
nanos = notEmpty.awaitNanos(nanos);
}
return dequeue();
} finally {
lock.unlock();
}
}
public E peek() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return itemAt(takeIndex); // null when queue is empty
} finally {
lock.unlock();
}
}
public int size() {
final ReentrantLock lock = this.lock;
lock.lock();
try {
return count;
} finally {
lock.unlock();
}
}
}
数组阻塞队列：一个lock，2个condition，放的时候放和取都不行，取的时候取和放都不行。为空了取的线程都在emptyCondition
等待，满了放的线程都在fullCondition上面等待，唤醒时候只唤醒一个线程。只能同时一个取或者放。
Condition的特性:
1.Condition中的await()方法相当于Object的wait()方法，Condition中的signal()方法相当于Object的notify()方法，Condition中的signalAll()相当于Object的notifyAll()方法。不同的是，Object中的这些方法是和同步锁捆绑使用的；而Condition是需要与互斥锁/共享锁捆绑使用的。
2.Condition它更强大的地方在于：能够更加精细的控制多线程的休眠与唤醒。对于同一个锁，我们可以创建多个Condition，在不同的情况下使用不同的Condition。
如果采用Object类中的wait(), notify(), notifyAll()实现该缓冲区，当向缓冲区写入数据之后需要唤醒"读线程"时，不可能通过notify()或notifyAll()明确的指定唤醒"读线程"，而只能通过notifyAll唤醒所有线程(但是notifyAll无法区分唤醒的线程是读线程，还是写线程)。 但是，通过Condition，就能明确的指定唤醒读线程。
链表阻塞队列：2个锁，2个confition，放的时候不能放可以取（也只是一个取），取的时候不能取可以放（只能一个放）。只能同时一个放一个取。都是通过count来平衡空和满的。
public class LinkedBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, java.io.Serializable {
static class Node<E> {
E item;
Node<E> next;
Node(E x) { item = x; }
}
private final int capacity;
private final AtomicInteger count = new AtomicInteger();
transient Node<E> head;
private transient Node<E> last;
private final ReentrantLock takeLock = new ReentrantLock();
private final Condition notEmpty = takeLock.newCondition();
private final ReentrantLock putLock = new ReentrantLock();
private final Condition notFull = putLock.newCondition();
private void signalNotEmpty() {
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
notEmpty.signal();
} finally {
takeLock.unlock();
}
}
private void signalNotFull() {
final ReentrantLock putLock = this.putLock;
putLock.lock();
try {
notFull.signal();
} finally {
putLock.unlock();
}
}
private void enqueue(Node<E> node) {
last = last.next = node;
}
private E dequeue() {
// assert takeLock.isHeldByCurrentThread();
// assert head.item == null;
Node<E> h = head;
Node<E> first = h.next;
h.next = h; // help GC
head = first;
E x = first.item;
first.item = null;
return x;
}
void fullyLock() {
putLock.lock();
takeLock.lock();
}
void fullyUnlock() {
takeLock.unlock();
putLock.unlock();
}
public LinkedBlockingQueue(int capacity) {
if (capacity <= 0) throw new IllegalArgumentException();
this.capacity = capacity;
last = head = new Node<E>(null);
}
public int size() {
return count.get();
}
public int remainingCapacity() {
return capacity - count.get();
}
public void put(E e) throws InterruptedException {
if (e == null) throw new NullPointerException();
int c = -1;
Node<E> node = new Node<E>(e);
final ReentrantLock putLock = this.putLock;
final AtomicInteger count = this.count;
putLock.lockInterruptibly();
try {
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, 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)//等待时间还没有就返回false
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 boolean offer(E e) {
if (e == null) throw new NullPointerException();
final AtomicInteger count = this.count;
if (count.get() == capacity) //是满的直接返回
return false;
int c = -1;
Node<E> node = new Node<E>(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 E take() throws InterruptedException {
E x;
int c = -1;
final AtomicInteger count = this.count;
final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly();
try {
while (count.get() == 0) {
notEmpty.await();
}
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally {
takeLock.unlock();
}
if (c == capacity)
signalNotFull();
return x;
}
public E poll(long timeout, TimeUnit unit) throws InterruptedException {
E x = null;
int c = -1;
long nanos = unit.toNanos(timeout);
final AtomicInteger count = this.count;
final ReentrantLock takeLock = this.takeLock;
takeLock.lockInterruptibly();
try {
while (count.get() == 0) {
if (nanos <= 0) //等到时间返回
return null;
nanos = notEmpty.awaitNanos(nanos);
}
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
} finally {
takeLock.unlock();
}
if (c == capacity)
signalNotFull();
return x;
}
public E poll() {
final AtomicInteger count = this.count;
if (count.get() == 0)
return null; //直接返回
E x = null;
int c = -1;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
if (count.get() > 0) {
x = dequeue();
c = count.getAndDecrement();
if (c > 1)
notEmpty.signal();
}
} finally {
takeLock.unlock();
}
if (c == capacity)
signalNotFull();
return x;
}
public E peek() {
if (count.get() == 0)
return null;
final ReentrantLock takeLock = this.takeLock;
takeLock.lock();
try {
Node<E> first = head.next;
if (first == null)
return null;
else
return first.item;
} finally {
takeLock.unlock();
}
}
public boolean remove(Object o) {
if (o == null) return false;
fullyLock();//读写都锁住
try {
for (Node<E> trail = head, p = trail.next;
p != null;
trail = p, p = p.next) {
if (o.equals(p.item)) {
unlink(p, trail);
return true;
}
}
return false;
} finally {
fullyUnlock();
}
}
public boolean contains(Object o) {
if (o == null) return false;
fullyLock();//读写都锁住
try {
for (Node<E> p = head.next; p != null; p = p.next)
if (o.equals(p.item))
return true;
return false;
} finally {
fullyUnlock();
}
}
public Object[] toArray() {
fullyLock();
try {
int size = count.get();
Object[] a = new Object[size];
int k = 0;
for (Node<E> p = head.next; p != null; p = p.next)
a[k++] = p.item;
return a;
} finally {
fullyUnlock();
}
}