package programmingexample4;
import java.util.Iterator;
/**
* Interface for a bag. A bag is similar to a set but allows for
* duplicates.
*
* @author Robert Clifton-Everest
*/
public interface Bag
/**
* Adds a single copy of an element to the bag
* @param e The element to add
* @postcondition count(e) = old count(e) + 1
*/
public void add(E e);
/**
* Adds multiple copies of an element to the bag.
* @param e The element to add
* @param n The number of copies
* @precondition n >= 0
* @postcondition count(e) = old count(e) + n
*/
public void add(E e, int n);
/**
* Remove one copy of the given element from the bag.
* @param e
* @postcondition count(e) = max(old count(e) – 1, 0)
*/
public void remove(E e);
/**
* Remove multiple copies of an element from the bag, or all copies if there
* are not that many copies in the bag.
* @param e The element to remove
* @param n The number of copies to remove.
* @precondition n >= 0
* @postcondition count(e) = max(old count(e) – n, 0)
*/
public void remove(E e, int n);
/**
* Returns the number of times the given object occurs in the bag
* @param o The object to get the count of
* @return count
* @postcondition count >= 0
*/
public int count(Object o);
/**
* The total number of items in the bag
* @return size
* @postcondition size >= 0
*/
public int size();
/**
* The sum of this bag and the given bag. If e occurs N times
* in this bag and M times in the given bag then it will occur N+M times
* in the resultant bag.
* @param bag
* @return result
* @postcondition for all e, result.count(e) = count(e) + bag.count(e)
*/
public Bag
/**
* The iterator method. The iterator should yield a Count for each element
* that occurs at least once in the bag.
*/
public Iterator
}