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package org.hsqldb.lib;
/**
* Provides the HyperSQL interface for Heap ADT implementations.
*
* In this context, a Heap is simply a collection-like ADT that allows addition
* of elements and provides a way to remove the least element, given some
* implementation-dependent strategy for imposing an order over its
* elements.
*
* Typically, an HsqlHeap will be implemented as a tree-like structure that
* recursively guarantees a Heap Invariant, such that all nodes below
* the root are greater than the root, given some comparison strategy.
* This in turn provides the basis for an efficient implementation of ADTs such
* PriorityQueue, since Heap operations using the typical implementation are,
* in theory, guaranteed to be O(log n).
*
* This interface represents a pure queue with the same basic queue methods
* as {@code java.util.Queue} but without all the extra methods.
*
* @author Campbell Burnet (campbell-burnet@users dot sourceforge.net)
* @version 2.6.0
* @since 1.7.2
*/
public interface HsqlHeap {
/**
* Removes all of the elements from this Heap.
*/
void clear();
/**
* Retrieves whether this Heap is empty.
*
* @return boolean
*/
boolean isEmpty();
/**
* Retrieves whether this Heap is full.
*
* @return boolean
*/
boolean isFull();
/**
* Adds the specified element to this Heap.
*
* @param o The element to add
* @throws IllegalArgumentException if the implementation does
* not accept elements of the supplied type (optional)
* @throws RuntimeException if the implementation
* dictates that this Heap is not currently accepting additions
* or that this Heap is currently full (optional)
* @return boolean
*/
boolean add(E o);
/**
* Retrieves the least element from this Heap, without removing it.
*
* @return the least element from this Heap
*/
E peek();
/**
* Retrieves the least element from this Heap, removing it in the process.
*
* @return the least element from this Heap
*/
E remove();
/**
* Retrieves the number of elements currently in this Heap.
*
* @return the number of elements currently in this Heap
*/
int size();
}