libjava/java/util/Dictionary.java

/* Dictionary.java -- an abstract (and essentially worthless) 
   class which is Hashtable's superclass
   Copyright (C) 1998 Free Software Foundation, Inc.

This file is part of GNU Classpath.

GNU Classpath is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Classpath is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Classpath; see the file COPYING.  If not, write to the
Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA.

As a special exception, if you link this library with other files to
produce an executable, this library does not by itself cause the
resulting executable to be covered by the GNU General Public License.
This exception does not however invalidate any other reasons why the
executable file might be covered by the GNU General Public License. */


package java.util;

/**
 * A Dictionary maps keys to values; <i>how</i> it does that is
 * implementation-specific.
 * 
 * This is an abstract class which has really gone by the wayside.
 * People at Javasoft are probably embarrassed by it.  At this point,
 * it might as well be an interface rather than a class, but it remains
 * this poor, laugable skeleton for the sake of backwards compatibility.
 * At any rate, this was what came before the <pre>Map</pre> interface 
 * in the Collections framework.
 *
 * @author      Jon Zeppieri
 */
public abstract class Dictionary extends Object
{
  /** returns an Enumeration of the values in this Dictionary */
  public abstract Enumeration elements();

  /** 
   * returns the value associated with the supplied key, or null
   * if no such value exists
   *
   * @param    key      the key to use to fetch the value
   */
  public abstract Object get(Object key);

  /** returns true IFF there are no elements in this Dictionary (size() == 0) */
  public abstract boolean isEmpty();

  /** returns an Enumeration of the keys in this Dictionary */
  public abstract Enumeration keys();

  /**
   * inserts a new value into this Dictionary, located by the
   * supllied key; note: Dictionary's subclasses (all 1 of them)
   * do not support null keys or values (I can only assume this
   * would have been more general) 
   *
   * @param      key      the key which locates the value
   * @param      value    the value to put into the Dictionary
   */
  public abstract Object put(Object key, Object value);

  /**
   * removes fro the Dictionary the value located by the given key
   *
   * @param       key      the key used to locate the value to be removed
   */
  public abstract Object remove(Object key);

  /** returns the number of values currently in this Dictionary */
  public abstract int size();
}