package map;
import container.*;
import java.util.Iterator;

public interface Map {

  /** Return the number of entries. */
  public int size();

  /** Are there any entries? */
  public boolean isEmpty();

  /** Add an entry with key k and value v. 
   * Returns the new entry.
   */
  public Entry insert(Object k, Object v) throws InvalidKeyException;

  /** If the map contains an entry with key k,
   * return such an entry, otherwise return null.
   * Why don't we just return the value?  Because 
   * then if we returned null it might mean either "no 
   * entry" or "entry with value null."  Also, because by
   * returning the entry, we make it possible for the
   * user to replace the entry's value.  
   */
  public Entry find(Object k) throws InvalidKeyException;

  /** If the dictionary contains an entry with key k,
   * remove and return such an entry, otherwise return null.
   * The reason to return the whole entry is for consistency
   * with find().
   */
  public Entry remove(Object k) throws InvalidKeyException;

  /** Return an iterator over all entries in the dictionary. 
   *
   * (Note: As for any Iterator, its next() method returns Objects,
   * but they can be downcast to Entries.)
   */
  public Iterator entries();

  /** Replaces the value of an entry in the dictionary. 
   * Returns the old value.  
   */
  public Object replaceValue(Entry e, Object v);
}