Here you can find the source of addAll(final Collection
public static <T> Collection<T> addAll(final Collection<T> collection, final T[] items)
//package com.java2s; //License from project: LGPL import java.util.*; public class Main { public static <T> Collection<T> addAll(final Collection<T> collection, final T[] items) { if (null != items) { if (null != collection) { Collections.addAll(collection, items); }/*w ww.j ava 2 s. c o m*/ } return collection; } }