Here you can find the source of join(final String[] in, final String sep)
public static String join(final String[] in, final String sep)
//package com.java2s; /*//www .j ava 2 s . c o m * Copyright (c) 2012 Jeremy N. Harton * * 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.Arrays; import java.util.List; public class Main { public static String join(final String[] in, final String sep) { return join(Arrays.asList(in), sep); } public static String join(final List<String> in, String sep) { if (sep == null) sep = ""; if (in.size() == 0) return ""; final StringBuilder out = new StringBuilder(); for (final String s : in) { out.append(sep).append(s); } return out.delete(0, sep.length()).toString(); } }