android directory size

I need to calculate the physical size of a directory. The naive algorithm to do that could be :

public static long getFolderSize(File dir) {
long size = 0;
for (File file : dir.listFiles()) {
    if (file.isFile()) {
        System.out.println(file.getName() + " " + file.length());
        size += file.length();
    }
    else
        size += getFolderSize(file);
}
return size;
}

but how to deal with symbolic links ?