Java Path Relative makeRelativePath(File from, File to)

Description

make Relative Path

License

Apache License

Declaration

public static String makeRelativePath(File from, File to)

Method Source Code

//package com.java2s;
/*//from w w  w.j a va  2s .  c o m
 * Copyright 2008 Google Inc.
 *
 * 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.File;

import java.io.IOException;

public class Main {
    public static String makeRelativePath(File from, File to) {
        File f = makeRelativeFile(from, to);
        return (f != null ? f.getPath() : null);
    }

    public static String makeRelativePath(File from, String to) {
        File f = makeRelativeFile(from, new File(to));
        return (f != null ? f.getPath() : null);
    }

    /**
     * Attempts to make a path relative to a particular directory.
     *
     * @param from the directory from which 'to' should be relative
     * @param to an absolute path which will be returned so that it is relative to
     *          'from'
     * @return the relative path, if possible; null otherwise
     */
    public static File makeRelativeFile(File from, File to) {

        // Keep ripping off directories from the 'from' path until the 'from' path
        // is a prefix of the 'to' path.
        //
        String toPath = tryMakeCanonical(to).getAbsolutePath();
        File currentFrom = tryMakeCanonical(from.isDirectory() ? from : from.getParentFile());

        int numberOfBackups = 0;
        while (currentFrom != null) {
            String currentFromPath = currentFrom.getPath();
            if (toPath.startsWith(currentFromPath)) {
                // Found a prefix!
                //
                break;
            } else {
                ++numberOfBackups;
                currentFrom = currentFrom.getParentFile();
            }
        }

        if (currentFrom == null) {
            // Cannot make it relative.
            //
            return null;
        }

        // Find everything to the right of the common prefix.
        //
        String trailingToPath = toPath.substring(currentFrom.getAbsolutePath().length());
        if (currentFrom.getParentFile() != null && trailingToPath.length() > 0) {
            trailingToPath = trailingToPath.substring(1);
        }

        File relativeFile = new File(trailingToPath);
        for (int i = 0; i < numberOfBackups; ++i) {
            relativeFile = new File("..", relativeFile.getPath());
        }

        return relativeFile;
    }

    /**
     * Attempts to find the canonical form of a file path.
     *
     * @return the canonical version of the file path, if it could be computed;
     *         otherwise, the original file is returned unmodified
     */
    public static File tryMakeCanonical(File file) {
        try {
            return file.getCanonicalFile();
        } catch (IOException e) {
            return file;
        }
    }
}

Java Path Relative makeRelativePath(File from, File to)

Description

License

Declaration

Method Source Code

Related