Here you can find the source of join(Iterable items)
public static String join(Iterable<?> items)
//package com.java2s; /*//from w ww. j a v a 2 s.c om * Copyright (c) 2011 Evident Solutions Oy * * Permission is hereby granted, free of charge, to any person obtaining a copy * of this software and associated documentation files (the "Software"), to deal * in the Software without restriction, including without limitation the rights * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell * copies of the Software, and to permit persons to whom the Software is * furnished to do so, subject to the following conditions: * * The above copyright notice and this permission notice shall be included in * all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN * THE SOFTWARE. */ import java.util.*; public class Main { public static String join(Iterable<?> items) { return join(items, ""); } public static String join(Iterable<?> items, String separator) { StringBuilder sb = new StringBuilder(); for (Iterator<?> it = items.iterator(); it.hasNext();) { sb.append(it.next()); if (it.hasNext()) sb.append(separator); } return sb.toString(); } }