Java Path Relative Get getRelativePath(File home, File f)

Description

get relative path of File 'f' with respect to 'home' directory example : home = /a/b/c f = /a/d/e/x.txt s = getRelativePath(home,f) = ../../d/e/x.txt home = "/a/b/c" file = "/a/b/c/d/e.txt" relative path = "d/e.txt" home = "/a/b/c" file = "/a/d/f/g.txt" relative path = "../../d/f/g.txt"

License

BSD License

Parameter

Parameter	Description
home	base path, should be a directory, not a file, or it doesn't make sense
f	file to generate path for

Return

path from home to f as a string

Declaration

public static String getRelativePath(File home, File f)

Method Source Code

//package com.java2s;
/**//from  ww  w . j a v  a  2  s . c  om
 * <p>
 * Utilities for manipulating Paths, Files, Directories, etc.
 * </p>
 * <p>
 * <span class="BSDLicense"> This software is distributed under the <a
 * href="http://hci.stanford.edu/research/copyright.txt">BSD License</a>.</span>
 * </p>
 * 
 * @author <a href="http://graphics.stanford.edu/~ronyeh">Ron B Yeh</a> (ronyeh(AT)cs.stanford.edu)
 */

import java.io.File;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

public class Main {
    /**
     * get relative path of File 'f' with respect to 'home' directory example : home = /a/b/c f = /a/d/e/x.txt
     * s = getRelativePath(home,f) = ../../d/e/x.txt
     * 
     * home = "/a/b/c" file = "/a/b/c/d/e.txt" relative path = "d/e.txt"
     * 
     * home = "/a/b/c" file = "/a/d/f/g.txt" relative path = "../../d/f/g.txt"
     * 
     * @author David M. Howard
     * @param home
     *            base path, should be a directory, not a file, or it doesn't make sense
     * @param f
     *            file to generate path for
     * @return path from home to f as a string
     */
    public static String getRelativePath(File home, File f) {
        List<String> homelist;
        List<String> filelist;
        String s;

        homelist = getPathList(home);
        filelist = getPathList(f);
        s = matchPathLists(homelist, filelist);

        return s;
    }

    /**
     * break a path down into individual elements and add to a list. example : if a path is /a/b/c/d.txt, the
     * breakdown will be [d.txt,c,b,a]
     * 
     * @author David M. Howard
     * @param f
     *            input file
     * @return a List collection with the individual elements of the path in reverse order
     */
    private static List<String> getPathList(File f) {
        List<String> l = new ArrayList<String>();
        File r;
        try {
            r = f.getCanonicalFile();
            while (r != null) {
                l.add(r.getName());
                r = r.getParentFile();
            }
        } catch (IOException e) {
            e.printStackTrace();
            l = null;
        }
        return l;
    }

    /**
     * figure out a string representing the relative path of 'f' with respect to 'r'
     * 
     * @author David M. Howard
     * 
     * @param r
     *            home path
     * @param f
     *            path of file
     */
    private static String matchPathLists(List<String> r, List<String> f) {
        int i;
        int j;
        String s;
        // start at the beginning of the lists
        // iterate while both lists are equal
        s = "";
        i = r.size() - 1;
        j = f.size() - 1;

        // first eliminate common root
        while ((i >= 0) && (j >= 0) && (r.get(i).equals(f.get(j)))) {
            i--;
            j--;
        }

        // for each remaining level in the home path, add a ..
        for (; i >= 0; i--) {
            s += ".." + File.separator;
        }

        // for each level in the file path, add the path
        for (; j >= 1; j--) {
            s += f.get(j) + File.separator;
        }

        // file name
        s += f.get(j);
        return s;
    }
}