Example of functional-style ‘map’ in Java. Isn’t it revolting? :)

Map.java

package net.noiseinstitute.lambda;

import java.util.ArrayList;
import java.util.Collection;
import java.util.List;

public class Map {

    public static <T,U> List<U> map (Collection<T> collection, MapCallback<T,U> callback) {
        List<U> list = new ArrayList<U>();
        for (T value: collection) {
            list.push(callback.mapValue(value));
        }
        return list;
    }

    static interface MapCallback<T,U> {
        U mapValue (T value);
    }

    static void main (String args) {
        List<Integer> list = new ArrayList<Integer>();
        list.add(1);
        list.add(2);
        list.add(3);

        list = map(list, new MapCallback<Integer,Integer>() {
            @Override
            public Integer mapValue(Integer value) {
                return value * 2;
            }
        });

        // list now contains {2, 4, 6}
        System.out.println(list.get(2)); // 6
    }

}