Queue常用类解析之PriorityQueue_queue.priorityqueue-优快云博客

本文深入解析了PriorityQueue，一种基于最小堆数据结构的优先级队列。详细介绍了其属性，如队列元素以完全二叉树形式存储，并探讨了插入、扩容、删除元素以及上浮和下沉等核心操作的实现原理。

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PriorityQueue称作优先队列，与普通队列先进先出不同，优先级队列中优先级最高的元素最先出列。

一、属性

//默认容量，初始化队列没有穿容量参数时使用
private static final int DEFAULT_INITIAL_CAPACITY = 11;

 /**
  * Priority queue represented as a balanced binary heap: the two
  * children of queue[n] are queue[2*n+1] and queue[2*(n+1)].  The
  * priority queue is ordered by comparator, or by the elements'
  * natural ordering, if comparator is null: For each node n in the
  * heap and each descendant d of n, n <= d.  The element with the
  * lowest value is in queue[0], assuming the queue is nonempty.
  */
  //元素数组
 transient Object[] queue; // non-private to simplify nested class access

 /**
  * The number of elements in the priority queue.
  */
  //元素数量
 private int size = 0;

 /**
  * The comparator, or null if priority queue uses elements'
  * natural ordering.
  */
  //优先级的比较器，仅当元素为Comparable时可以为null
 private final Comparator<? super E> com