1 /* 2 * Licensed to the Apache Software Foundation (ASF) under one or more 3 * contributor license agreements. See the NOTICE file distributed with 4 * this work for additional information regarding copyright ownership. 5 * The ASF licenses this file to You under the Apache License, Version 2.0 6 * (the "License"); you may not use this file except in compliance with 7 * the License. You may obtain a copy of the License at 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 */ 17 18 package java.util; 19 20 /** 21 * <strong>Note: Do not use this class since it is obsolete. Please use the 22 * {@link Map} interface for new implementations.</strong> 23 * <p> 24 * Dictionary is an abstract class which is the superclass of all classes that 25 * associate keys with values, such as {@code Hashtable}. 26 * 27 * @see Hashtable 28 * @since 1.0 29 */ 30 public abstract class Dictionary<K, V> { 31 /** 32 * Constructs a new instance of this class. 33 */ 34 public Dictionary() { 35 } 36 37 /** 38 * Returns an enumeration on the elements of this dictionary. 39 * 40 * @return an enumeration of the values of this dictionary. 41 * @see #keys 42 * @see #size 43 * @see Enumeration 44 */ 45 public abstract Enumeration<V> elements(); 46 47 /** 48 * Returns the value which is associated with {@code key}. 49 * 50 * @param key 51 * the key of the value returned. 52 * @return the value associated with {@code key}, or {@code null} if the 53 * specified key does not exist. 54 * @see #put 55 */ 56 public abstract V get(Object key); 57 58 /** 59 * Returns true if this dictionary has no key/value pairs. 60 * 61 * @return {@code true} if this dictionary has no key/value pairs, 62 * {@code false} otherwise. 63 * @see #size 64 */ 65 public abstract boolean isEmpty(); 66 67 /** 68 * Returns an enumeration on the keys of this dictionary. 69 * 70 * @return an enumeration of the keys of this dictionary. 71 * @see #elements 72 * @see #size 73 * @see Enumeration 74 */ 75 public abstract Enumeration<K> keys(); 76 77 /** 78 * Associate {@code key} with {@code value} in this dictionary. If {@code 79 * key} exists in the dictionary before this call, the old value in the 80 * dictionary is replaced by {@code value}. 81 * 82 * @param key 83 * the key to add. 84 * @param value 85 * the value to add. 86 * @return the old value previously associated with {@code key} or {@code 87 * null} if {@code key} is new to the dictionary. 88 * @see #elements 89 * @see #get 90 * @see #keys 91 */ 92 public abstract V put(K key, V value); 93 94 /** 95 * Removes the key/value pair with the specified {@code key} from this 96 * dictionary. 97 * 98 * @param key 99 * the key to remove. 100 * @return the associated value before the deletion or {@code null} if 101 * {@code key} was not known to this dictionary. 102 * @see #get 103 * @see #put 104 */ 105 public abstract V remove(Object key); 106 107 /** 108 * Returns the number of key/value pairs in this dictionary. 109 * 110 * @return the number of key/value pairs in this dictionary. 111 * @see #elements 112 * @see #keys 113 */ 114 public abstract int size(); 115 } 116
