LinkedBlockingQueue

介紹

LinkedBlockingQueue實現BlockingQueue接口.

JDK中位置:java.util.concurrent包下,該包爲併發包,一樣LinkedBlockingQueue自身實現了併發處理,使用的是存取鎖的方式.

自身還實現了讀寫分離鎖，真正高效併發。

下面直接切入源碼.

構造器

默認構造器沒有參數

public LinkedBlockingQueue() {   

 this(Integer.MAX_VALUE);//默認長度    

}    

指定長度構造器

public LinkedBlockingQueue(int capacity) {   

 if (capacity <= 0) throw new IllegalArgumentException();    

 this.capacity = capacity;    

 last = head = new Node<E>(null);    

}    

存方法

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();//得到put鎖，不能有兩個線程同時存入數據    

 try {    

 while (count.get() == capacity) {//判斷隊列是否已滿.若是隊列已滿則一直等待     

 notFull.await();    

 }    

 enqueue(node);//存入隊列尾    

 c = count.getAndIncrement();//計數器自增    

 if (c + 1 < capacity)    

 notFull.signal();    

 } finally {    

 putLock.unlock();//釋放put鎖    

 }    

 if (c == 0)    

 signalNotEmpty();    

}

取方法

public E take() throws InterruptedException {   

 E x;    

 int c = -1;    

 final AtomicInteger count = this.count;    

 final ReentrantLock takeLock = this.takeLock;    

 takeLock.lockInterruptibly();//不能同時有兩個線程獲取數據    

 try {    

 while (count.get() == 0) {//判斷隊列是否爲空.若是爲空則一直循環等待     

 notEmpty.await();    

 }    

 x = dequeue();//取出隊列頭    

 c = count.getAndDecrement();//計數器自減    

 if (c > 1)    

 notEmpty.signal();    

 } finally {    

 takeLock.unlock();//釋放tack鎖    

 }    

 if (c == capacity)    

 signalNotFull();    

 return x;    

}