Dictionary class in java
In java, the package java.util contains a class called Dictionary which works like a Map. The Dictionary is an abstract class used to store and manage elements in the form of a pair of key and value.
The Dictionary stores data as a pair of key and value. In the dictionary, each key associates with a value. We can use the key to retrieve the value back when needed.
🔔 The Dictionary class is no longer in use, it is obsolete.
🔔 As Dictionary is an abstract class we can not create its object. It needs a child class like Hashtable.
The Dictionary class in java has the following methods.
| S. No. | Methods with Description |
|---|---|
| 1 | Dictionary( ) It's a constructor. |
| 2 |
Object put(Object key, Object value)
Inserts a key and its value into the dictionary. Returns null on success; returns the previous value associated with the key if the key is already exist. |
| 3 |
Object remove(Object key)
It returns the value associated with given key and removes the same; Returns null if the key does not exist. |
| 4 |
Object get(Object key)
It returns the value associated with given key; Returns null if the key does not exist. |
| 5 |
Enumeration keys( )
Returns an enumeration of the keys contained in the dictionary. |
| 6 |
Enumeration elements( )
Returns an enumeration of the values contained in the dictionary. |
| 7 |
boolean isEmpty( )
It returns true if dictionary has no elements; otherwise returns false. |
| 8 |
int size( )
It returns the total number of elements in the dictionary. |
Let's consider an example program to illustrate methods of Dictionary class.
import java.util.*;
public class DictionaryExample {
public static void main(String args[]) {
Dictionary dict = new Hashtable();
dict.put(1, "Rama");
dict.put(2, "Seetha");
dict.put(3, "Heyansh");
dict.put(4, "Varshith");
dict.put(5, "Manutej");
System.out.println("Dictionary\n=> " + dict);
// keys()
System.out.print("\nKeys in Dictionary\n=> ");
for (Enumeration i = dict.keys(); i.hasMoreElements();)
{
System.out.print(" " + i.nextElement());
}
// elements()
System.out.print("\n\nValues in Dictionary\n=> ");
for (Enumeration i = dict.elements(); i.hasMoreElements();)
{
System.out.print(" " + i.nextElement());
}
//get()
System.out.println("\n\nValue associated with key 3 => " + dict.get(3));
System.out.println("Value associated with key 30 => " + dict.get(30));
//size()
System.out.println("\nDictionary has " + dict.size() + " elements");
//isEmpty()
System.out.println("\nIs Dictionary empty? " + dict.isEmpty());
}
}
When we execute the above code, it produce the following output.
