Java tutorial
//package com.java2s; import java.util.ArrayList; import java.util.Comparator; import java.util.List; public class Main { public static <T extends Comparator<T>> List<T> intersection(List<T> array1, List<T> array2) { if (isEmpty(array1) || isEmpty(array2)) { return null; } List<T> targets = new ArrayList<T>(); for (T item : array1) { if (array2.contains(item)) { targets.add(item); } } return targets; } public static <T extends Comparator<T>> Boolean isEmpty(List<T> collection) { return collection == null || collection.isEmpty(); } }