LinkedBlockingQueue 特点
LinkedBlockingQueue 通常叫做链表阻塞队列，从命名可以知道，其底层数据是链表，且队列是可阻塞的。LinkedBlockingQueue 的特点：
基于链表实现的阻塞队列，底层的数据结构为链表
基于链表实现先入先出的队列，新元素放在队尾，从队头部获取元素
链表大小在初始化的时候可以设置大小，默认为 Integer 的最大值
可以使用 Iterator 进行迭代
属性
源码：
public class LinkedBlockingQueue<E> extends AbstractQueue<E> implements BlockingQueue<E>, java.io.Serializable { private static final long serialVersionUID = -6903933977591709194L; /** * Linked list node class */ static class Node<E> { E item;
/** * One of: * - the real successor Node * - this Node, meaning the successor is head.next * - null, meaning there is no successor (this is the last node) */ Node<E> next;
Node(E x) { item = x; } } /** The capacity bound, or Integer.MAX_VALUE if none */ private final int capacity;
/** Current number of elements */ private final AtomicInteger count = new AtomicInteger();
/** * Head of linked list. * Invariant: head.item == null */ transient Node<E> head;
/** * Tail of linked list. * Invariant: last.next == null */ private transient Node<E> last;
/** 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();
......}
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static class Node<E> 表示链表的元素节点
Node<E> next; 表示当前元素指向的下一个节点，如果为 null，则表示当前节点为最后一个节点
private final int capacity;链表的容量，默认 Integer.MAX_VALUE
private final AtomicInteger count = new AtomicInteger();链表已有元素大小，使用 AtomicInteger，所以是线程安全的
transient Node<E> head; 链表头
private transient Node<E> last;链表尾
private final ReentrantLock takeLock = new ReentrantLock(); take 时的锁
private final Condition notEmpty = takeLock.newCondition();take 的条件队列
private final ReentrantLock putLock = new ReentrantLock();put 时的锁
private final Condition notFull = putLock.newCondition();put 的条件队列
总结：设计了两把锁，一个是 take 锁，一个是 put 锁，目的是为了让两个操作互相不干扰，同步进行
初始化
源码：
public LinkedBlockingQueue() { this(Integer.MAX_VALUE); }
public LinkedBlockingQueue(int capacity) { if (capacity <= 0) throw new IllegalArgumentException(); this.capacity = capacity; last = head = new Node<E>(null); }
public LinkedBlockingQueue(Collection<? extends E> c) { this(Integer.MAX_VALUE); final ReentrantLock putLock = this.putLock; putLock.lock(); // Never contended, but necessary for visibility try { int n = 0; for (E e : c) { if (e == null) throw new NullPointerException(); if (n == capacity) throw new IllegalStateException("Queue full"); enqueue(new Node<E>(e)); ++n; } count.set(n); } finally { putLock.unlock(); } }
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源码中提供了三种初始化的方式：第一种：使用默认的 Integer 的最大值进行初始化第二种：指定链表容量大小初始化第三章：使用已有集合数据进行初始化
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