Here you can find the source of join(String delimeter, Collection
static <T> String join(String delimeter, Collection<T> items)
//package com.java2s; //License from project: Open Source License import java.util.*; public class Main { static <T> String join(String delimeter, Collection<T> items) { boolean isFirst = true; String rval = ""; for (T i : items) { if (!isFirst) rval += delimeter;//from w ww. j a v a2s .co m else isFirst = false; rval += i.toString(); } return rval; } }