Check if file is in (sub)directory

Question

I would like to check whether an existing file is in a specific directory or a subdirectory of that.

I have two File objects.

File dir;
File file;
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Answer 1

This method looks pretty solid:

/**
 * Checks, whether the child directory is a subdirectory of the base 
 * directory.
 *
 * @param base the base directory.
 * @param child the suspected child directory.
 * @return true, if the child is a subdirectory of the base directory.
 * @throws IOException if an IOError occured during the test.
 */
public boolean isSubDirectory(File base, File child)
    throws IOException {
    base = base.getCanonicalFile();
    child = child.getCanonicalFile();

    File parentFile = child;
    while (parentFile != null) {
        if (base.equals(parentFile)) {
            return true;
        }
        parentFile = parentFile.getParentFile();
    }
    return false;
}

Source

It is similar to the solution by dacwe but doesn't use recursion (though that shouldn't make a big difference in this case).