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/** |
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* 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 |
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* specified as for {@link TreeSet} and {@link TreeMap}: Elements are ordered |
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* elements according to an order specified at construction time, which is |
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* 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 |
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* 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 |
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* 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 |
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* which of elements is returned. |
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* elements are tied for least value, no guarantees are made as to |
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* 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 |
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* the array used 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, |
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* <p>A priority queue has a <i>capacity</i>. The capacity is the size of |
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* 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 queue, |
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* its capacity grows automatically. The details of the growth policy are not |
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* specified. |
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* |
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*<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> |
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* 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 |
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* <tt>contains</tt> methods; and constant time for the <tt>peek</tt>, |
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* <tt>element</tt>, and <tt>size</tt> methods. |
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* <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>). |
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* |
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* <p>This class is a member of the |
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* <a href="{@docRoot}/../guide/collections/index.html"> |
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* 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 |
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* 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 |
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* of n, d, n <= d. |
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* comparator is null: For each node n in the heap and each descendant d |
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* 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 |
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* nonempty). A one-based array is used in preference to the traditional |
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* zero-based array to simplify parent and child calculations. |
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* The element with the lowest value is in queue[1], assuming the queue is |
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* nonempty. (A one-based array is used in preference to the traditional |
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* zero-based array to simplify parent and child calculations.) |
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* |
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* 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) |
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* that orders its elements according to their natural ordering. |
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* that orders its elements according to their natural ordering (using <tt>Comparable</tt>.) |
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*/ |
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public PriorityQueue() { |
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this(DEFAULT_INITIAL_CAPACITY); |
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/** |
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* Create a new priority queue with the specified initial capacity |
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* that orders its elements according to their natural ordering. |
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* 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. |
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*/ |
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* 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' |
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* 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 |
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* <tt>Sorted</tt> interface, the priority queue is ordered according to |
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* natural order. If the specified collection does not implement |
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* <tt>Sorted</tt>, the priority queue is ordered according to |
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* its elements' natural order. |
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* |
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* @param initialElements the collection whose elements are to be placed |
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|
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/** |
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* 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 |
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* 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. |
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* |
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* @return the minimal element from this priority queue if it contains |
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|
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/** |
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* 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 |
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* 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 |
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* 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 |
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* specified element (or equivalently, if this collection changed as a |
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* result of the call). |
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* |
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* @param o element to be removed from this collection, if present. |
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* @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 |
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* call |
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* @throws ClassCastException if the specified element cannot be compared |
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/** |
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* 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 |
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* would be returned by a call to <tt>peek</tt>. |
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* elements of the priority queue will be returned by this iterator in the |
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* 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. |
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*/ |
