package edu.stanford.nlp.util;import java.util.*;/** Heap: It's the heap interface. *  These heaps implement a decreaseKey operation, which requires *  a separate Object to Index map, and for objects to be unique in the Heap. * * An interface cannot specify constructors, but it is nevertheless *  expected that an implementation of this interface has a constructor *  that takes a Comparator, which is used for ordering ("scoring") *  objects: *        <code>public Heap(Comparator cmp) {}</code> * *  @author Dan Klein *  @version 12/14/00 */public interface Heap {  /**   * Returns the minimum object, then removes that object from the heap.   *   * @return the minimum object   */  public Object extractMin();  /**    *  Returns the minimum Object in this heap. The heap is not modified.   *   *  @return the minimum object   */  public Object min();  /**   * Adds the object to the heap.  If the object is in the heap, this   * should act as a decrease-key (if the new version has better   * priority) or a no-op (otherwise).   *   * @param o a new element   * @return true, always   */  public boolean add(Object o);    /**   * The number of elements currently in the heap.   *   * @return the heap's size   */  public int size();  /**   * Returns true iff the heap is empty.   *   * @return a <code>boolean</code> value   */  public boolean isEmpty();  /**   * Raises the priority of an object in the heap.  This works in a   * somewhat unusual way -- the object <code>o</code> should have   * changed with respect to the comparator passed in to the heap on   * construction.  However, it should NOT have changed with respect   * to its equals() method.  This is unlike the Java SortedSet where   * the comparator should be consistent with equals(); here they   * should not match.   *   * @param o an <code>Object</code> value which has changed wrt the heap's ordering   * @return the cost of the decrease-key operation, for analysis   */  public int decreaseKey(Object o); // should be void; int for analysis  /**   * Returns an iterator over its elements, in order.   *   * @return an <code>Iterator</code> value   */  public Iterator iterator();}