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| 1 | /* | ||
| 2 | * Copyright (c) 1995, 2004, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package java.util; | ||
| 27 | |||
| 28 | /** | ||
| 29 | * The <code>Dictionary</code> class is the abstract parent of any | ||
| 30 | * class, such as <code>Hashtable</code>, which maps keys to values. | ||
| 31 | * Every key and every value is an object. In any one <tt>Dictionary</tt> | ||
| 32 | * object, every key is associated with at most one value. Given a | ||
| 33 | * <tt>Dictionary</tt> and a key, the associated element can be looked up. | ||
| 34 | * Any non-<code>null</code> object can be used as a key and as a value. | ||
| 35 | * <p> | ||
| 36 | * As a rule, the <code>equals</code> method should be used by | ||
| 37 | * implementations of this class to decide if two keys are the same. | ||
| 38 | * <p> | ||
| 39 | * <strong>NOTE: This class is obsolete. New implementations should | ||
| 40 | * implement the Map interface, rather than extending this class.</strong> | ||
| 41 | * | ||
| 42 | * @author unascribed | ||
| 43 | * @see java.util.Map | ||
| 44 | * @see java.lang.Object#equals(java.lang.Object) | ||
| 45 | * @see java.lang.Object#hashCode() | ||
| 46 | * @see java.util.Hashtable | ||
| 47 | * @since JDK1.0 | ||
| 48 | */ | ||
| 49 | public abstract | ||
| 50 | class Dictionary<K,V> { | ||
| 51 | /** | ||
| 52 | * Sole constructor. (For invocation by subclass constructors, typically | ||
| 53 | * implicit.) | ||
| 54 | */ | ||
| 55 | public Dictionary() { | ||
| 56 | } | ||
| 57 | |||
| 58 | /** | ||
| 59 | * Returns the number of entries (distinct keys) in this dictionary. | ||
| 60 | * | ||
| 61 | * @return the number of keys in this dictionary. | ||
| 62 | */ | ||
| 63 | abstract public int size(); | ||
| 64 | |||
| 65 | /** | ||
| 66 | * Tests if this dictionary maps no keys to value. The general contract | ||
| 67 | * for the <tt>isEmpty</tt> method is that the result is true if and only | ||
| 68 | * if this dictionary contains no entries. | ||
| 69 | * | ||
| 70 | * @return <code>true</code> if this dictionary maps no keys to values; | ||
| 71 | * <code>false</code> otherwise. | ||
| 72 | */ | ||
| 73 | abstract public boolean isEmpty(); | ||
| 74 | |||
| 75 | /** | ||
| 76 | * Returns an enumeration of the keys in this dictionary. The general | ||
| 77 | * contract for the keys method is that an <tt>Enumeration</tt> object | ||
| 78 | * is returned that will generate all the keys for which this dictionary | ||
| 79 | * contains entries. | ||
| 80 | * | ||
| 81 | * @return an enumeration of the keys in this dictionary. | ||
| 82 | * @see java.util.Dictionary#elements() | ||
| 83 | * @see java.util.Enumeration | ||
| 84 | */ | ||
| 85 | abstract public Enumeration<K> keys(); | ||
| 86 | |||
| 87 | /** | ||
| 88 | * Returns an enumeration of the values in this dictionary. The general | ||
| 89 | * contract for the <tt>elements</tt> method is that an | ||
| 90 | * <tt>Enumeration</tt> is returned that will generate all the elements | ||
| 91 | * contained in entries in this dictionary. | ||
| 92 | * | ||
| 93 | * @return an enumeration of the values in this dictionary. | ||
| 94 | * @see java.util.Dictionary#keys() | ||
| 95 | * @see java.util.Enumeration | ||
| 96 | */ | ||
| 97 | abstract public Enumeration<V> elements(); | ||
| 98 | |||
| 99 | /** | ||
| 100 | * Returns the value to which the key is mapped in this dictionary. | ||
| 101 | * The general contract for the <tt>isEmpty</tt> method is that if this | ||
| 102 | * dictionary contains an entry for the specified key, the associated | ||
| 103 | * value is returned; otherwise, <tt>null</tt> is returned. | ||
| 104 | * | ||
| 105 | * @return the value to which the key is mapped in this dictionary; | ||
| 106 | * @param key a key in this dictionary. | ||
| 107 | * <code>null</code> if the key is not mapped to any value in | ||
| 108 | * this dictionary. | ||
| 109 | * @exception NullPointerException if the <tt>key</tt> is <tt>null</tt>. | ||
| 110 | * @see java.util.Dictionary#put(java.lang.Object, java.lang.Object) | ||
| 111 | */ | ||
| 112 | abstract public V get(Object key); | ||
| 113 | |||
| 114 | /** | ||
| 115 | * Maps the specified <code>key</code> to the specified | ||
| 116 | * <code>value</code> in this dictionary. Neither the key nor the | ||
| 117 | * value can be <code>null</code>. | ||
| 118 | * <p> | ||
| 119 | * If this dictionary already contains an entry for the specified | ||
| 120 | * <tt>key</tt>, the value already in this dictionary for that | ||
| 121 | * <tt>key</tt> is returned, after modifying the entry to contain the | ||
| 122 | * new element. <p>If this dictionary does not already have an entry | ||
| 123 | * for the specified <tt>key</tt>, an entry is created for the | ||
| 124 | * specified <tt>key</tt> and <tt>value</tt>, and <tt>null</tt> is | ||
| 125 | * returned. | ||
| 126 | * <p> | ||
| 127 | * The <code>value</code> can be retrieved by calling the | ||
| 128 | * <code>get</code> method with a <code>key</code> that is equal to | ||
| 129 | * the original <code>key</code>. | ||
| 130 | * | ||
| 131 | * @param key the hashtable key. | ||
| 132 | * @param value the value. | ||
| 133 | * @return the previous value to which the <code>key</code> was mapped | ||
| 134 | * in this dictionary, or <code>null</code> if the key did not | ||
| 135 | * have a previous mapping. | ||
| 136 | * @exception NullPointerException if the <code>key</code> or | ||
| 137 | * <code>value</code> is <code>null</code>. | ||
| 138 | * @see java.lang.Object#equals(java.lang.Object) | ||
| 139 | * @see java.util.Dictionary#get(java.lang.Object) | ||
| 140 | */ | ||
| 141 | abstract public V put(K key, V value); | ||
| 142 | |||
| 143 | /** | ||
| 144 | * Removes the <code>key</code> (and its corresponding | ||
| 145 | * <code>value</code>) from this dictionary. This method does nothing | ||
| 146 | * if the <code>key</code> is not in this dictionary. | ||
| 147 | * | ||
| 148 | * @param key the key that needs to be removed. | ||
| 149 | * @return the value to which the <code>key</code> had been mapped in this | ||
| 150 | * dictionary, or <code>null</code> if the key did not have a | ||
| 151 | * mapping. | ||
| 152 | * @exception NullPointerException if <tt>key</tt> is <tt>null</tt>. | ||
| 153 | */ | ||
| 154 | abstract public V remove(Object key); | ||
| 155 | } | ||