Java Path Relative Get getRelativePath(File parent, File child)

Description

Returns the relative path to a file with respect to a parent directory.

License

Open Source License

Parameter

Parameter	Description
parent	the assumed parent (a directory)
child	the assumed child of the parent (a directory or a file)

Exception

Parameter	Description
IOException	If caused by File#getCanonicalFile.

Return

the relative path from parent to file as File object, or null if the parent and the child are not related.

Declaration

public static File getRelativePath(File parent, File child) throws IOException 

Method Source Code

//package com.java2s;
//      Licensed under the terms of GNU General Public License v3.

import java.io.File;
import java.io.IOException;

public class Main {
    /**/*from  w  w w.  jav  a 2 s .  c om*/
     * Returns the relative path to a file with respect to a parent directory.
     * The method can be used to determine whether the given File objects
     * form a parent-child relationship. If they do form such a relationship,
     * the relative path from the parent to the child is returned. If they
     * don't form a parent-child relationship, {@code null} is returned.
     *
     * @param parent the assumed parent (a directory)
     * @param child the assumed child of the parent (a directory or a file)
     *
     * @return the relative path from parent to file as {@code File} object,
     * or {@code null} if the parent and the child are not related.
     *
     * @throws IOException If caused by {@link File#getCanonicalFile}.
     */
    public static File getRelativePath(File parent, File child) throws IOException {
        // Canonicalize parent
        parent = parent.getCanonicalFile();
        // Canonicalize the child into a local variable
        File file = child.getCanonicalFile();

        // Create a relative path to the child. The relative path is
        // constructed sequentially during the loop. The construction
        // begins with the most nested directory and then adds new directory
        // the front of the existing path.
        File rval = new File(file.getName());

        // Repeat while the file has a parent.
        while ((file = file.getParentFile()) != null) {
            // If the current directory equals to the parent directory,
            // then we're done.
            if (parent.equals(file)) {
                return rval;
            }
            // Prepend with the current directory
            rval = new File(file.getName(), rval.getPath());
        } // while
          // The loop traversed the whole hierarchy up, and parent was not
          // encountered. It must be concluded that the parent wasn't really
          // a parent of the child.
        return null;
    }
}

Related

1. getRelativePath(File home, File f)
2. getRelativePath(File home, File f)
3. getRelativePath(File home, File f)
4. getRelativePath(File original, File directory)
5. getRelativePath(File parent, File child)
6. getRelativePath(File parent, File f)
7. getRelativePath(File parentDirectory, File file)
8. getRelativePath(File path, File base)
9. getRelativePath(File path, File basePath)