Functions on Iterables :: Transformer

public interface Transformer<I, O>
{
   public O transform(I item);
}

public class Functional
{
   /**
    * Transforms Iterable<I> into Iterable<O> using a Transformer<I, O>
    */

   public static <I, O> Iterable<O> transform(final Iterable<I> iterable,
                                              final Transformer<I, O> transformer)
   {
      if (iterable == null)
         throw new NullPointerException();
      if (transformer == null)
         throw new NullPointerException();

      return new Iterable<O>()
      {
         @Override
         public Iterator<O> iterator()
         {
            final Iterator<I> iterator = iterable.iterator();

            return new Iterator<O>()
            {
               @Override
               public boolean hasNext()
               {
                  return iterator.hasNext();
               }

               @Override
               public O next()
               {
                  return transformer.transform(iterator.next());
               }

               @Override
               public void remove()
               {
                  iterator.remove();
               }
            };
         }
      };
   }
}

Example:

Transformer<String, Integer> textToNumber = new Transformer<String, Integer>()
{
   public Integer transform(String text)
   {
      return Integer.valueOf(text);
   }
};

Iterable<String> data = ...;

for(Integer number: transform(data, textToNumber))
{
   System.out.println("number: "+number.intValue());
}