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From: Eric Sosman <esosman@comcast-dot-net.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: How convert Iterator into Enumeration
Date: Wed, 28 Nov 2012 13:22:34 -0500
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On 11/28/2012 6:55 AM, Jan Burse wrote:
> Dear All,
>
> Is there a fast way to have an Enumeration from a HashMap?
>
> I am trying to reimplement the HttpServletRequest interface,
> and I am trying to use a HashMap for parameters and attributes.
> I guess this is valid when my web application doesn't use
> a HttpServletRequest concurrently, right? Or might the web
> server populate it concurrently?
>
> Now I am stuck here:
>
>      /**
>       * <p>Retrieve the parameter names.</p>
>       *
>       * @return The names.
>       */
>      public Enumeration<String> getParameterNames() {
>          return parametermap.keys();
>      }

	public Enumeration<String> getParameterNames() {
	    return new Enumeration<String>() {
	        private final Iterator<String> iter =
	            myHashMap.iterator();
	        @Override
	        public boolean hasMoreElements() {
	            return iter.hasNext();
	        }
	        @Override
	        public String nextElement() {
	            return iter.next();
	        }
	    };
	}

If you do this sort of thing a lot write yourself a utility
class implementing Enumeration<T>, with a constructor that
takes an Iterator<T>.  A companion class wrapping an Iterator<T>
around an Enumeration<T> is equally easy to write, and might
also be handy.  (I'm a little surprised that Snoracle doesn't
provide such wrappers -- or maybe they do, but under names
that have escaped my notice.)

-- 
Eric Sosman
esosman@comcast-dot-net.invalid