数据结构——java Queue类

定义

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队列是一种特殊的线性表，它只允许在表的前端进行删除操作，而在表的后端进行插入操作。

LinkedList类实现了Queue接口，因此我们可以把LinkedList当成Queue来用

图例

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Queue本身是一种先入先出的模型(FIFO)，和我们日常生活中的排队模型很类似。根据不同的实现，他们主要有数组和链表两种实现形式。如下图：

与队列相关的类的关系图如下：

常用方法

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序号	方法名	描述
1	boolean add(E e)	将指定的元素插入到队列中。
2	Object element()	检索该队列的头。
	boolean offer(E e)	将指定元素插入到该队列中（在该队列容量之内）。
3	Object peek()	检索该队列的头，如果该队列为空返回null。
4	Object poll()	检索并删除该队列的头，如果该队列为空返回null。
5	Object remove()	检索并删除该队列的头。

源码

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 package java.util;

 public interface Queue<E> extends Collection<E> {
     /**
      * Inserts the specified element into this queue if it is possible to do so
      * immediately without violating capacity restrictions, returning
      * {@code true} upon success and throwing an {@code IllegalStateException}
      * if no space is currently available.
      *
      * @param e the element to add
      * @return {@code true} (as specified by {@link Collection#add})
      * @throws IllegalStateException if the element cannot be added at this
      *         time due to capacity restrictions
      * @throws ClassCastException if the class of the specified element
      *         prevents it from being added to this queue
      * @throws NullPointerException if the specified element is null and
      *         this queue does not permit null elements
      * @throws IllegalArgumentException if some property of this element
      *         prevents it from being added to this queue
      */
     boolean add(E e);

     /**
      * Inserts the specified element into this queue if it is possible to do
      * so immediately without violating capacity restrictions.
      * When using a capacity-restricted queue, this method is generally
      * preferable to {@link #add}, which can fail to insert an element only
      * by throwing an exception.
      *
      * @param e the element to add
      * @return {@code true} if the element was added to this queue, else
      *         {@code false}
      * @throws ClassCastException if the class of the specified element
      *         prevents it from being added to this queue
      * @throws NullPointerException if the specified element is null and
      *         this queue does not permit null elements
      * @throws IllegalArgumentException if some property of this element
      *         prevents it from being added to this queue
      */
     boolean offer(E e);

     /**
      * Retrieves and removes the head of this queue.  This method differs
      * from {@link #poll poll} only in that it throws an exception if this
      * queue is empty.
      *
      * @return the head of this queue
      * @throws NoSuchElementException if this queue is empty
      */
     E remove();

     /**
      * Retrieves and removes the head of this queue,
      * or returns {@code null} if this queue is empty.
      *
      * @return the head of this queue, or {@code null} if this queue is empty
      */
     E poll();

     /**
      * Retrieves, but does not remove, the head of this queue.  This method
      * differs from {@link #peek peek} only in that it throws an exception
      * if this queue is empty.
      *
      * @return the head of this queue
      * @throws NoSuchElementException if this queue is empty
      */
     E element();

     /**
      * Retrieves, but does not remove, the head of this queue,
      * or returns {@code null} if this queue is empty.
      *
      * @return the head of this queue, or {@code null} if this queue is empty
      */
     E peek();
 }

参考：http://blog.csdn.net/u010617952/article/details/51726789