Difference between enum and Enumeration

Question

Is there any difference between enum datatype and Enumeration Interface. I have become confused between the two.

I got my answer that they aren't related but that brings me to another question.

We cannot instantiate interface . So what is the significance of this line

Enumeration days = dayNames.elements();

Heres the complete code containing that line

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

public class EnumerationTester {

   public static void main(String args[]) {
      Enumeration days;
      Vector dayNames = new Vector();
      dayNames.add("Sunday");
      dayNames.add("Monday");
      dayNames.add("Tuesday");
      dayNames.add("Wednesday");
      dayNames.add("Thursday");
      dayNames.add("Friday");
      dayNames.add("Saturday");
      days = dayNames.elements();
      while (days.hasMoreElements()){
         System.out.println(days.nextElement()); 
      }
   }
}

Answer 1

Enumeration is an interface : An object that implements the Enumeration interface generates a series of elements, one at a time. Successive calls to the nextElement method return successive elements of the series.

For example, to print all elements of a Vector<E> v:

for (Enumeration<E> e = v.elements(); e.hasMoreElements();)
       System.out.println(e.nextElement());

enum is a data type: An enum type is a special data type that enables for a variable to be a set of predefined constants. The variable must be equal to one of the values that have been predefined for it.

For example, you would specify a days-of-the-week enum type as:

 public enum Day {
        SUNDAY, MONDAY, TUESDAY, WEDNESDAY,
        THURSDAY, FRIDAY, SATURDAY 
    }

   public static void main(String[] args)
  {
     System.out.ptintln(Day.SUNDAY);  // print SUNDAY
  }

Your Second Question:

We cannot instantiate interface . So what is the significance of this line

Enumeration days = dayNames.elements();

dayNames is a Vector, a collection just like List. (There are differences, but that is beyond the scope of the question.). However, when daynames.elements() is called, it returns an enumeration of the components of vector daynames. The returned Enumeration object will generate all items added to this vector. The first item generated is the item at index 0, then the item at index 1, and so on.