Here you can find the source of addAll(Collection
public static <T> void addAll(Collection<T> dest, Iterator<T> src)
//package com.java2s; /*// w ww. j av a 2s . co m * Copyright 2008-2016 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Licensed under the Apache License, Version 2.0 (the "License"). * You may not use this file except in compliance with the License. * A copy of the License is located at: * * http://aws.amazon.com/apache2.0/ * * or in the "license" file accompanying this file. This file is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific * language governing permissions and limitations under the License. */ import java.util.Collection; import java.util.Iterator; public class Main { public static <T> void addAll(Collection<T> dest, Iterator<T> src) { if (src != null) { while (src.hasNext()) { T value = src.next(); dest.add(value); } } } }