In this article, we will discuss Enumeration interface in detail

1. Key points about Enumeration:

• Enumeration is a legacy interface
• introduced in Java 1.0 version

2. Enumeration interface:

• Enumeration interface allows to read or get element/object one-by-one from collection object
• This interface is part of legacy collection
• Only legacy collection classes like Vector or Properties or Hashtable are allowed to iterate over collection objects using Enumeration interface
• Present in java.util package

Q) How to get Enumeration object ?

• We can create Enumeration object using elements() method present in all legacy classes
• Legacy classes: Hashtable, Vector, Stack, Properties classes and Dictionary abstract class
• For example,

Vector v = new Vector(); 
Enumeration e = v.elements(); // v is a legacy class Vector

3. Limitation of Enumeration interface:

• Enumeration interface applicable only for legacy classes like Vector, Properties or Hashtable
• all classes part of Java 1.0 version
• It cannot be used with new collection framework classes like ArrayList or TreeSet (introduced in Java 1.2)
• By enumerating, we can only read collection objects
• but no other operations can be performed like remove element from collection object

4. Enumeration interface methods:

5. Enumeration examples:

EnumerationExample.java

package in.bench.resources.java.collection;

import java.util.Enumeration;
import java.util.Vector;

public class EnumerationExample {

	public static void main(String[] args) {

		// creating Vector object of type String
		Vector<String> vec = new Vector<String>();

		// adding elements to Vector object
		vec.addElement("Sundar Pichai");
		vec.addElement("Satya Nadella");
		vec.addElement("Shiv Nadar");
		vec.addElement("Shantanu Narayen");
		vec.addElement("Francisco D’Souza");

		// creating enumeration reference
		Enumeration<String> ceo = vec.elements();

		// enumerating using while loop
		while (ceo.hasMoreElements()){
			System.out.println(ceo.nextElement());
		}
	}
}

Output:

Sundar Pichai
Satya Nadella
Shiv Nadar
Shantanu Narayen
Francisco D’Souza

Related Articles:

• Iterator
• List Iterator
• Enumeration v/s Iterator v/s ListIterator

References:

• https://docs.oracle.com/javase/tutorial/collections/intro/
• https://docs.oracle.com/javase/tutorial/collections/interfaces/collection.html
• https://docs.oracle.com/javase/7/docs/api/java/util/Collection.html
• https://docs.oracle.com/javase/tutorial/collections/interfaces/list.html
• https://docs.oracle.com/javase/8/docs/api/java/util/List.html
• https://docs.oracle.com/javase/8/docs/api/java/util/ArrayList.html
• https://docs.oracle.com/javase/8/docs/api/java/util/Vector.html
• https://docs.oracle.com/javase/7/docs/api/java/util/Enumeration.html

Happy Coding !!
Happy Learning !!