Java tutorial
//package com.java2s; import java.util.Collection; import java.util.HashSet; import java.util.Set; public class Main { public static <T> Collection<T> union(Collection<T> a, Collection<T> b) { Set<T> set = new HashSet<T>(a); for (T obj : b) { if (!set.contains(obj)) { set.add(obj); } } return set; } }