Dictionary is an abstract class that represents a key/value storage repository and operates much like Map.
Given a key and value, you can store the value in a Dictionary object.
Once the value is stored, you can retrieve it by using its key.
Like a map, a dictionary can be thought of as a list of key/value pairs.
Dictionary is classified as obsolete, we should use Map.
With the advent of JDK 5, Dictionary was made generic. It is declared as shown here:
class Dictionary<K, V>
Here, K specifies the type of keys, and V specifies the type of values.
The abstract methods defined by Dictionary are listed in the following table.
| Method | Purpose |
|---|---|
| Enumeration<V> | elements() Returns an enumeration of the values contained in the dictionary. |
| V | get(Object key) Returns the object that contains the value associated with key. If key is not in the dictionary, a null object is returned. |
| boolean | isEmpty() Returns true if the dictionary is empty, and returns false if it contains at least one key. |
| Enumeration<K> | keys() Returns an enumeration of the keys contained in the dictionary. |
| V | put(K key, V value) Inserts a key and its value into the dictionary. Returns null if key is not already in the dictionary; returns the previous value associated with key if key is already in the dictionary. |
| V | remove(Object key) Removes key and its value. Returns the value associated with key. If key is not in the dictionary, a null is returned. |
| int | size() Returns the number of entries in the dictionary. |
To add a key and a value, use the put() method.
Use get() to retrieve the value of a given key.
The keys and values can each be returned as an Enumeration by the keys() and elements() methods, respectively.
The size() method returns the number of key/value pairs stored in a dictionary, and isEmpty() returns true when the dictionary is empty.
You can use the remove() method to delete a key/value pair.
Note: The Dictionary class is obsolete.
You should implement the Map interface to obtain key/value storage functionality.
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