/*
* @(#)Dictionary.java 1.1 95/08/07
*
* Copyright (c) 1995 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for NON-COMMERCIAL purposes and without fee is hereby
* granted provided that this copyright notice appears in all copies. Please
* refer to the file "copyright.html" for further important copyright and
* licensing information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
* SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
* IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
* OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY
* LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR
* ITS DERIVATIVES.
*/
package java.util;
/**
* The Dictionary class is the abstract parent of Hashtable, which maps
* keys to values. Any object can be used as a key and/or value.
*
* @see java.util.Hashtable
* @see java.lang.Object#hashCode
* @see java.lang.Object#equals
* @version 1.1, 07 Aug 1995
*/
public abstract
class Dictionary {
/**
* Returns the number of elements contained within the Dictionary.
*/
abstract public int size();
/**
* Returns true if the Dictionary contains no elements.
*/
abstract public boolean isEmpty();
/**
* Returns an enumeration of the Dictionary's keys.
* @see Dictionary#elements
* @see Enumeration
*/
abstract public Enumeration keys();
/**
* Returns an enumeration of the elements. Use the Enumeration methods
* on the returned object to fetch the elements sequentially.
* @see Dictionary#keys
* @see Enumeration
*/
abstract public Enumeration elements();
/**
* Gets the object associated with the specified key in the Dictionary.
* @param key the key in the hash table
* @returns the element for the key or null if the key
* is not defined in the hash table.
* @see Dictionary#put
*/
abstract public Object get(Object key);
/**
* Puts the specified element into the Dictionary, using the specified
* key. The element may be retrieved by doing a get() with the same
* key. The key and the element cannot be null.
* @param key the specified hashtable key
* @param value the specified element
* @return the old value of the key, or null if it did not have one.
* @exception NullPointerException If the value of the specified
* element is null.
* @see Dictionary#get
*/
abstract public Object put(Object key, Object value);
/**
* Removes the element corresponding to the key. Does nothing if the
* key is not present.
* @param key the key that needs to be removed
* @return the value of key, or null if the key was not found.
*/
abstract public Object remove(Object key);
}