Java tutorial
//package com.java2s; import java.util.ArrayList; import java.util.Collection; public class Main { public static <T> Collection<T> setDiff(Collection<T> itemsToStartWith, Collection<T> itemsToSubtract) { Collection<T> retval = new ArrayList<T>(); if (itemsToStartWith == null) return new ArrayList<T>(); retval.addAll(itemsToStartWith); // make copy so you don't mutate original if (itemsToSubtract != null) retval.removeAll(itemsToSubtract); return retval; } }