Here you can find the source of join(String dir, String subDir)
public static String join(String dir, String subDir)
//package com.java2s; /*//from ww w.jav a 2 s .c o m Copyright (c) 2012 IBM Corp. Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License 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.io.*; public class Main { public static String join(String dir, String subDir) { dir = ensureSlash(dir); if (subDir.startsWith(File.separator)) { subDir = subDir.substring(1); } return dir + subDir; } public static String ensureSlash(String dirPath) { if (dirPath.endsWith(File.separator)) { return dirPath; } return dirPath + File.separator; } }