A simple Java FP list map

Following on the comments I received on my previous entry about doing a bit of Java functional programming style, I made a very simple class to map a list. I'm following the style of what I have seen in the apache collections utilities. See previous post.

First note that I am doing it without generics (I'm stuck with jdk1.4.2 at work), so for some this would be old style Java programming.

Here's the utility class.
ListUtils.java

package fp;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ListUtils {
static public List map(List elements, Applier applier) {
List result = new ArrayList();
for (Iterator it = elements.iterator(); it.hasNext();) {
Object element = it.next();
result.add(applier.apply(element));
}
return result;
}
}


And the interface used by the utility class.
Applier.java

package fp;

public interface Applier {
public Object apply(Object element);
}


Here's a client code example.

WithPoints.java

package domino;

public interface WithPoints {
public Integer getPoints();
}


Domino.java

package domino;

public class Domino implements WithPoints {
private Integer points;

public Domino(int points) {
this.points = new Integer(points);
}

public Integer getPoints() {
return points;
}
}


And finally!

package domino;

import fp.Applier;
import fp.ListUtils;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Main {

public static void main(String[] args) {
List dominoes = new ArrayList();
dominoes.add(new Domino(1));
dominoes.add(new Domino(2));
dominoes.add(new Domino(3));

List points = ListUtils.map(dominoes, new Applier() {
public Object apply(Object domino) {
return ((WithPoints) domino).getPoints();
}
});

System.out.println(points); // [1, 2, 3]
}
}


So this time around, I did get a new list instead of transforming a list but I still think the simple iterator style is clearer and it avoids using a "utility class" for doing something really simple.

Iterator style

List points;
for (Iterator iter = Dominoes.iterator(); iter.hasNext();) {
points.add((WithPoints) iter.next().getPoints());
}


And of course, Scala still is neater for me 8)

val points = dominoes map (x => x.points)