import java.util.Iterator;
/**
   An interface for a dictionary with distinct search keys.
   Search keys and associated values are not null.
   @author Frank M. Carrano
   @author Timothy M. Henry
   @version 5.0
*/
public interface DictionaryInterface<K, V>
{
   /** Adds a new entry to this dictionary. If the given search key already
       exists in the dictionary, replaces the corresponding value.
       @param key    An object search key of the new entry.
       @param value  An object associated with the search key.
       @return  Either null if the new entry was added to the dictionary
                or the value that was associated with key if that value
                was replaced. */
   public V add(K key, V value);
   
   /** Removes a specific entry from this dictionary.
       @param key  An object search key of the entry to be removed.
       @return  Either the value that was associated with the search key
                or null if no such object exists. */
   public V remove(K key);
   
   /** Retrieves from this dictionary the value associated with a given
       search key.
       @param key  An object search key of the entry to be retrieved.
       @return  Either the value that is associated with the search key
                or null if no such object exists. */
   public V getValue(K key);
   
   /** Sees whether a specific entry is in this dictionary.
       @param key  An object search key of the desired entry.
       @return  True if key is associated with an entry in the dictionary. */
   public boolean contains(K key);
   
   /** Creates an iterator that traverses all search keys in this dictionary.
       @return  An iterator that provides sequential access to the search
                keys in the dictionary. */
   public Iterator<K> getKeyIterator();
   
   /** Creates an iterator that traverses all values in this dictionary.
       @return  An iterator that provides sequential access to the values
                in this dictionary. */
   public Iterator<V> getValueIterator();
   
   /** Sees whether this dictionary is empty.
       @return  True if the dictionary is empty. */
   public boolean isEmpty();
   
   /** Gets the size of this dictionary.
       @return  The number of entries (key-value pairs) currently
                in the dictionary. */
   public int getSize();
   
   /** Removes all entries from this dictionary. */
   public void clear();
} // end DictionaryInterface