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/** 
/** 
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* An unbounded priority queue based on a priority heap. This queue orders 
* An unbounded priority queue based on a priority heap. This queue orders 
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* elements according to the order specified at creation time. This order is 
* elements according to an order specified at construction time, which is 
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* specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered 
* specified in the same manner as {@link TreeSet} and {@link TreeMap}: elements are ordered 
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* either according to their <i>natural order</i> (see {@link Comparable}), or 
* either according to their <i>natural order</i> (see {@link Comparable}), or 
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* according to a {@link Comparator}, depending on which constructor is used. 
* according to a {@link Comparator}, depending on which constructor is used. 
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* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the 
* The {@link #peek}, {@link #poll}, and {@link #remove} methods return the 
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* minimal element with respect to the specified ordering. If multiple 
* minimal element with respect to the specified ordering. If multiple 
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* these elements are tied for least value, no guarantees are made as to 
* elements are tied for least value, no guarantees are made as to 
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* which of elements is returned. 
* which of these elements is returned. 
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* 
* 
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* <p>Each priority queue has a <i>capacity</i>. The capacity is the size of 
* <p>A priority queue has a <i>capacity</i>. The capacity is the size of 
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* the array used to store the elements on the queue. It is always at least 
* the array used internally to store the elements on the queue. It is always at least 
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* as large as the queue size. As elements are added to a priority list, 
* as large as the queue size. As elements are added to a priority queue, 
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* its capacity grows automatically. The details of the growth policy are not 
* its capacity grows automatically. The details of the growth policy are not 
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* specified. 
* specified. 
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* 
* 
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*<p>Implementation note: this implementation provides O(log(n)) time for 
*<p>Implementation note: this implementation provides O(log(n)) time for 
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* the <tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt> 
* the insertion methods (<tt>offer</tt>, <tt>poll</tt>, <tt>remove()</tt> and <tt>add</tt>) 
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* methods; linear time for the <tt>remove(Object)</tt> and 
* methods; linear time for the <tt>remove(Object)</tt> and 
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* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>, 
* <tt>contains(Object)</tt> methods; and constant time for the retrieval methods (<tt>peek</tt>, 
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* <tt>element</tt>, and <tt>size</tt> methods. 
* <tt>element</tt>, and <tt>size</tt>). 
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* 
* 
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* <p>This class is a member of the 
* <p>This class is a member of the 
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* <a href="{@docRoot}/../guide/collections/index.html"> 
* <a href="{@docRoot}/../guide/collections/index.html"> 
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* Priority queue represented as a balanced binary heap: the two children 
* Priority queue represented as a balanced binary heap: the two children 
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* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is 
* of queue[n] are queue[2*n] and queue[2*n + 1]. The priority queue is 
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* ordered by comparator, or by the elements' natural ordering, if 
* ordered by comparator, or by the elements' natural ordering, if 
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* comparator is null: For each node n in the heap, and each descendant 
* comparator is null: For each node n in the heap and each descendant d 
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* of n, d, n <= d. 
* of n, n <= d. 
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* 
* 
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* The element with the lowest value is in queue[1] (assuming the queue is 
* The element with the lowest value is in queue[1], assuming the queue is 
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* nonempty). A onebased array is used in preference to the traditional 
* nonempty. (A onebased array is used in preference to the traditional 
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* zerobased array to simplify parent and child calculations. 
* zerobased array to simplify parent and child calculations.) 
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* 
* 
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* queue.length must be >= 2, even if size == 0. 
* queue.length must be >= 2, even if size == 0. 
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*/ 
*/ 
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/** 
/** 
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* Create a new priority queue with the default initial capacity (11) 
* Create a new priority queue with the default initial capacity (11) 
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* that orders its elements according to their natural ordering. 
* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.) 
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*/ 
*/ 
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public PriorityQueue() { 
public PriorityQueue() { 
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this(DEFAULT_INITIAL_CAPACITY); 
this(DEFAULT_INITIAL_CAPACITY); 
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/** 
/** 
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* Create a new priority queue with the specified initial capacity 
* Create a new priority queue with the specified initial capacity 
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* that orders its elements according to their natural ordering. 
* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.) 
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* 
* 
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* @param initialCapacity the initial capacity for this priority queue. 
* @param initialCapacity the initial capacity for this priority queue. 
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*/ 
*/ 
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* implements the {@link Sorted} interface, the priority queue will be 
* implements the {@link Sorted} interface, the priority queue will be 
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* sorted according to the same comparator, or according to its elements' 
* sorted according to the same comparator, or according to its elements' 
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* natural order if the collection is sorted according to its elements' 
* natural order if the collection is sorted according to its elements' 
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* natural order. If the specified collection does not implement the 
* natural order. If the specified collection does not implement 
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* <tt>Sorted</tt> interface, the priority queue is ordered according to 
* <tt>Sorted</tt>, the priority queue is ordered according to 
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* its elements' natural order. 
* its elements' natural order. 
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* 
* 
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* @param initialElements the collection whose elements are to be placed 
* @param initialElements the collection whose elements are to be placed 
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143 
/** 
/** 
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* Remove and return the minimal element from this priority queue if 
* Remove and return the minimal element from this priority queue if 
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* it contains one or more elements, otherwise <tt>null</tt>. The term 
* it contains one or more elements, otherwise return <tt>null</tt>. The term 
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* <i>minimal</i> is defined according to this priority queue's order. 
* <i>minimal</i> is defined according to this priority queue's order. 
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* 
* 
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* @return the minimal element from this priority queue if it contains 
* @return the minimal element from this priority queue if it contains 
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157 
/** 
/** 
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* Return, but do not remove, the minimal element from the priority queue, 
* Return, but do not remove, the minimal element from the priority queue, 
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* or <tt>null</tt> if the queue is empty. The term <i>minimal</i> is 
* or return <tt>null</tt> if the queue is empty. The term <i>minimal</i> is 
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* defined according to this priority queue's order. This method returns 
* defined according to this priority queue's order. This method returns 
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* the same object reference that would be returned by by the 
* the same object reference that would be returned by by the 
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* <tt>poll</tt> method. The two methods differ in that this method 
* <tt>poll</tt> method. The two methods differ in that this method 
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* specified element (or equivalently, if this collection changed as a 
* specified element (or equivalently, if this collection changed as a 
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* result of the call). 
* result of the call). 
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* 
* 
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* @param o element to be removed from this collection, if present. 
* @param element the element to be removed from this collection, if present. 
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* @return <tt>true</tt> if this collection changed as a result of the 
* @return <tt>true</tt> if this collection changed as a result of the 
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* call 
* call 
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* @throws ClassCastException if the specified element cannot be compared 
* @throws ClassCastException if the specified element cannot be compared 
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210 
/** 
/** 
211 
* Returns an iterator over the elements in this priority queue. The 
* Returns an iterator over the elements in this priority queue. The 
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* first element returned by this iterator is the same element that 
* elements of the priority queue will be returned by this iterator in the 
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* would be returned by a call to <tt>peek</tt>. 
* order specified by the queue, which is to say the order they would be 
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* returned by repeated calls to <tt>poll</tt>. 
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* 
* 
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* @return an <tt>Iterator</tt> over the elements in this priority queue. 
* @return an <tt>Iterator</tt> over the elements in this priority queue. 
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*/ 
*/ 