Here you can find the source of join(List extends Object> olist, String glue)
public static String join(List<? extends Object> olist, String glue)
//package com.java2s; //License from project: Open Source License import java.util.*; public class Main { public static String join(List<? extends Object> olist, String glue) { return olist.toString(); }//from w w w. j a v a2 s . c om }