Question

I have a simple collections question. I have a Set<String> object. I want an Enumeration<String> of the Strings in that Set. I need an Enumeration<String> since I am overriding a method that specifically returns an Enumeration<String>. What is the cleanest/best way to go about it?

Answer 1

EDIT: There’s no need to write your own (although I’ll leave the implementation below for posterity) – see Kevin Bourrillion’s answer for the one in the JDK.

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If you really need an enumeration, could could use:

Enumeration<String> x = new Vector(set).elements();

It would be better to use Iterable<E> if at all possible though…

A better alternative is to write a small wrapper class around Iterator<E>. That way you don’t have to take a copy just to find an imlementation of Enumeration<E>:

import java.util.*;

class IteratorEnumeration<E> implements Enumeration<E>
{
    private final Iterator<E> iterator;
    
    public IteratorEnumeration(Iterator<E> iterator)
    {
        this.iterator = iterator;
    }
    
    public E nextElement() {
        return iterator.next();
    }
    
    public boolean hasMoreElements() {
        return iterator.hasNext();
    }
    
}


public class Test {
    public static void main(String[] args) {
        Set<String> set = new HashSet<String>(); 
        Enumeration<String> x = new IteratorEnumeration<String>(set.iterator());
    }
}