How to Use Enumeration to Display Elements of Hashtable in Java?

Hashtable class implements a hash table, which maps keys to values. Any non-null object can be used as a key or as a value. To successfully store and retrieve objects from a hashtable, the objects used as keys must implement the hashCode method and the equals method.  

Now here we can get the keys and values of a Hashtable as an Enumeration object using keys() and elements() method. We can obtain all keys and values respectively as an Enumeration object using Enumeration methods like hasMoreElements() and nextElement() we can read all keys and values corresponding to a Hashtable.

Example 1:

Java

// Java Program to Demonstrate Getting Values
// as an Enumeration of Hashtable class

import java.io.*;
import java.util.Enumeration;
import java.util.Hashtable;

// Main class
// EnumerationOnKeys
public class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating an empty hashtable
        Hashtable<Integer, String> ht
            = new Hashtable<Integer, String>();

        // Inserting key-value pairs into hash table
        // using put() method
        ht.put(1, "Geeks");
        ht.put(2, "for");
        ht.put(3, "Geeks");

        // Now creating an Enumeration object
        //  to read elements
        Enumeration e = ht.elements();

        // Condition holds true till there is
        // single key remaining

        // Printing elements of hashtable
        // using enumeration
        while (e.hasMoreElements()) {

            // Printing the current element
            System.out.println(e.nextElement());
        }
    }
}

Output

Geeks
for
Geeks

Example 2:

Java

// Java Program to Demonstrate Getting Keys
// as an Enumeration of Hashtable class

// Importing required classes
import java.io.*;
import java.util.*;

// Main class
class GFG {

    // Main driver method
    public static void main(String[] args)
    {
        // Creating an empty hashtable
        Hashtable<String, String> ht
            = new Hashtable<String, String>();

        // Inserting key-value pairs into hash table
        // using put() method
        ht.put("Name", "Rohan");
        ht.put("Age", "23");
        ht.put("Address", "India");
        ht.put("Article", "GeeksforGeeks");

        // Now creating an Enumeration object
        // to store keys
        Enumeration<String> e = ht.keys();

        // Condition holds true till there is
        // single key remaining
        while (e.hasMoreElements()) {

            // Getting key
            String key = e.nextElement();

            // Printing key and value corresponding to
            // that key
            System.out.println(key + ":" + ht.get(key));
        }
    }
}

Output

Name:Rohan
Article:GeeksforGeeks
Age:23
Address:India