import java.util.List;

import java.util.ArrayList;

public class ListHelper1 {

public interface MapFunction<A, B> {

public B apply(A input);

}

public static <A, B> List<B> map(List<A> list, MapFunction<A, B> func) {

List<B> mappedList = new ArrayList<>();

for (A elem : list) {

mappedList.add(func.apply(elem));

}

return mappedList;

}

public static void main(String[] args) {

List<String> words = new ArrayList<>();

words.add("hello");

words.add("goodbye");

words.add("hi");

List<Integer> lengths = map(words, new MapFunction<String, Integer>() {

public Integer apply(String str) {

return str.length();

}

});

// print out lengths 5, 7, 2

for (int length : lengths) {

System.out.println(length);

}

}

}