Source for java.util.Dictionary

   1: /* Dictionary.java -- an abstract (and essentially worthless) 
   2:    class which is Hashtable's superclass
   3:    Copyright (C) 1998, 2001, 2002, 2004 Free Software Foundation, Inc.
   4: 
   5: This file is part of GNU Classpath.
   6: 
   7: GNU Classpath is free software; you can redistribute it and/or modify
   8: it under the terms of the GNU General Public License as published by
   9: the Free Software Foundation; either version 2, or (at your option)
  10: any later version.
  11: 
  12: GNU Classpath is distributed in the hope that it will be useful, but
  13: WITHOUT ANY WARRANTY; without even the implied warranty of
  14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15: General Public License for more details.
  16: 
  17: You should have received a copy of the GNU General Public License
  18: along with GNU Classpath; see the file COPYING.  If not, write to the
  19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  20: 02110-1301 USA.
  21: 
  22: Linking this library statically or dynamically with other modules is
  23: making a combined work based on this library.  Thus, the terms and
  24: conditions of the GNU General Public License cover the whole
  25: combination.
  26: 
  27: As a special exception, the copyright holders of this library give you
  28: permission to link this library with independent modules to produce an
  29: executable, regardless of the license terms of these independent
  30: modules, and to copy and distribute the resulting executable under
  31: terms of your choice, provided that you also meet, for each linked
  32: independent module, the terms and conditions of the license of that
  33: module.  An independent module is a module which is not derived from
  34: or based on this library.  If you modify this library, you may extend
  35: this exception to your version of the library, but you are not
  36: obligated to do so.  If you do not wish to do so, delete this
  37: exception statement from your version. */
  38: 
  39: 
  40: package java.util;
  41: 
  42: /**
  43:  * A Dictionary maps keys to values; <i>how</i> it does that is
  44:  * implementation-specific.
  45:  * 
  46:  * This is an abstract class which has really gone by the wayside.
  47:  * People at Javasoft are probably embarrassed by it.  At this point,
  48:  * it might as well be an interface rather than a class, but it remains
  49:  * this poor, laughable skeleton for the sake of backwards compatibility.
  50:  * At any rate, this was what came before the {@link Map} interface 
  51:  * in the Collections framework.
  52:  *
  53:  * @author Jon Zeppieri
  54:  * @author Eric Blake (ebb9@email.byu.edu)
  55:  * @see Map
  56:  * @see Hashtable
  57:  * @since 1.0
  58:  * @status updated to 1.4
  59:  */
  60: public abstract class Dictionary<K, V>
  61: {
  62:   // WARNING: Dictionary is a CORE class in the bootstrap cycle. See the
  63:   // comments in vm/reference/java/lang/Runtime for implications of this fact.
  64: 
  65:   /**
  66:    * Sole constructor (often called implicitly).
  67:    */
  68:   public Dictionary()
  69:   {
  70:   }
  71: 
  72:   /**
  73:    * Returns an Enumeration of the values in this Dictionary.
  74:    *
  75:    * @return an Enumeration of the values
  76:    * @see #keys()
  77:    */
  78:   public abstract Enumeration<V> elements();
  79: 
  80:   /** 
  81:    * Returns the value associated with the supplied key, or null
  82:    * if no such value exists. Since Dictionaries are not allowed null keys
  83:    * or elements, a null result always means the key is not present.
  84:    *
  85:    * @param key the key to use to fetch the value
  86:    * @return the mapped value
  87:    * @throws NullPointerException if key is null
  88:    * @see #put(Object, Object)
  89:    */
  90:   public abstract V get(Object key);
  91: 
  92:   /**
  93:    * Returns true when there are no elements in this Dictionary.
  94:    *
  95:    * @return <code>size() == 0</code>
  96:    */
  97:   public abstract boolean isEmpty();
  98: 
  99:   /**
 100:    * Returns an Enumeration of the keys in this Dictionary
 101:    *
 102:    * @return an Enumeration of the keys
 103:    * @see #elements()
 104:    */
 105:   public abstract Enumeration<K> keys();
 106: 
 107:   /**
 108:    * Inserts a new value into this Dictionary, located by the
 109:    * supplied key. Dictionary does not support null keys or values, so
 110:    * a null return can safely be interpreted as adding a new key.
 111:    *
 112:    * @param key the key which locates the value
 113:    * @param value the value to put into the Dictionary
 114:    * @return the previous value of the key, or null if there was none
 115:    * @throws NullPointerException if key or value is null
 116:    * @see #get(Object)
 117:    */
 118:   public abstract V put(K key, V value);
 119: 
 120:   /**
 121:    * Removes from the Dictionary the value located by the given key. A null
 122:    * return safely means that the key was not mapped in the Dictionary.
 123:    *
 124:    * @param key the key used to locate the value to be removed
 125:    * @return the value associated with the removed key
 126:    * @throws NullPointerException if key is null
 127:    */
 128:   public abstract V remove(Object key);
 129: 
 130:   /**
 131:    * Returns the number of values currently in this Dictionary.
 132:    *
 133:    * @return the number of keys in the Dictionary
 134:    */
 135:   public abstract int size();
 136: } // class Dictionary