HsqlHeap


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30  
31  
32  package org.hsqldb.lib;
33  
34  /**
35   * Provides the base HSQLDB interface for Heap ADT implementations. <p>
36   *
37   * In this context, a Heap is simply a collection-like ADT that allows addition
38   * of elements and provides a way to remove the least element, given some
39   * implementation-dependent strategy for imposing an order over its
40   * elements. <p>
41   *
42   * Typically, an HsqlHeap will be implemented as a tree-like structure that
43   * recursively guarantees a <i>Heap Invariant</i>, such that all nodes below
44   * the root are greater than the root, given some comparison stragegy. <p>
45  
46   * This in turn provides the basis for an efficient implementation of ADTs such
47   * PriorityQueue, since Heap operations using the typical implementation are,
48   * in theory, guaranteed to be O(log n).
49   *
50   * @author boucherb@users
51   * @version 1.7.2
52   * @since 1.7.2
53   */
54  public interface HsqlHeap {
55  
56      /**
57       * Removes all of the elements from this Heap.
58       */
59      void clear();
60  
61      /**
62       * Retrieves whether this Heap is empty.
63       */
64      boolean isEmpty();
65  
66      /**
67       * Retrieves whether this Heap is full.
68       */
69      boolean isFull();
70  
71      /**
72       * Adds the specified element to this Heap.
73       *
74       * @param o The element to add
75       * @throws IllegalArgumentException if the implementation does
76       *      not accept elements of the supplied type (optional)
77       * throws RuntimeException if the implementation
78       *      dictates that this Heap is not currently accepting additions
79       *      or that this Heap is currently full (optional)
80       */
81      void add(Object   o) throws IllegalArgumentException  , RuntimeException  ;
82  
83      /**
84       * Retrieves the least element from this Heap, without removing it.
85       *
86       * @return the least element from this Heap
87       */
88      Object   peek();
89  
90      /**
91       * Retrieves the least element from this Heap, removing it in the process.
92       *
93       * @return the least element from this Heap
94       */
95      Object   remove();
96  
97      /**
98       * Retrieves the number of elements currently in this Heap.
99       *
100      * @return the number of elements currently in this Heap
101      */
102     int size();
103 }
104
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