Here you can find the source of getRelativePath(String targetPath, String basePath, String pathSeparator)
public static String getRelativePath(String targetPath, String basePath, String pathSeparator)
//package com.java2s; /*//from w w w . jav a2s. com * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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.File; import java.util.regex.Pattern; public class Main { public static String getRelativePath(String targetPath, String basePath, String pathSeparator) { File f = new File(targetPath); boolean isDir = f.isDirectory(); // We need the -1 argument to split to make sure we get a trailing // "" token if the base ends in the path separator and is therefore // a directory. We require directory paths to end in the path // separator -- otherwise they are indistinguishable from files. String[] base = basePath.split(Pattern.quote(pathSeparator), -1); String[] target = targetPath.split(Pattern.quote(pathSeparator), 0); // First get all the common elements. Store them as a string, // and also count how many of them there are. String common = ""; int commonIndex = 0; for (int i = 0; i < target.length && i < base.length; i++) { if (target[i].equals(base[i])) { common += target[i] + pathSeparator; commonIndex++; } else break; } if (commonIndex == 0) { // not even a single common path element. This most // likely indicates differing drive letters, like C: and D:. // These paths cannot be relativized. Return the target path. return targetPath; } String relative = ""; if (base.length == commonIndex) { // Comment this out if you prefer that a relative path not start with ./ relative = "." + pathSeparator; } else { int numDirsUp = base.length - commonIndex - (isDir ? 0 : 1); /* only subtract 1 if it is a file. */ // The number of directories we have to backtrack is the length of // the base path MINUS the number of common path elements, minus // one because the last element in the path isn't a directory. for (int i = 1; i <= (numDirsUp); i++) { relative += ".." + pathSeparator; } } //if we are comparing directories if (targetPath.length() > common.length()) { //it's OK, it isn't a directory relative += targetPath.substring(common.length()); } return relative; } }