MultiMap.java

/** A map interface that associates a key with multiple values.

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 PT_COPYRIGHT_VERSION_2
 COPYRIGHTENDKEY

 */
package ptolemy.data.ontologies.util;

import java.util.Map;

//////////////////////////////////////////////////////////////////////////
//// MultiMap

/**
A map that associates a key with multiple values.

Similar to MultiSet, MultiMap is a generalization of a abstract
data structure (Map). Like Map, MultiMap does not allow duplicate
keys. It associates a collection of objects to each key. Putting
a new object under a key adds to the associated collection.
Likewise, removing a object removes from the collection.

Several things are open to the implementation classes. First is the
ordering of the collection of all contained values. Second, ordering
within the collection is also open to the implementation class.
Each collection may or may not contain duplicates. For example, a
implementation class may use HashSets to represent the collections. This
effectively eliminate all duplicates but gives no ordering guarantee.
Although it is rare, but one can also imagine having a hybrid
implementation where each collection provide different guarantees
depending on the key that they map under.

 @author Man-Kit Leung
 @version $Id$
 @since Ptolemy II 7.1
 @Pt.ProposedRating Red (mankit)
 @Pt.AcceptedRating Red (mankit)
 */

public interface MultiMap extends Map {

    ///////////////////////////////////////////////////////////////////
    ////                         public methods                    ////

    /**
     * Remove a specified value from the map.
     * @param key The specified key.
     * @param object The specified object to remove from the collection.
     * @return The removed item, or null if the item
     *  does not exist.
     */
    public Object remove(Object key, Object object);

}