/** * Make a path relative with respect to a root path. absPath is always assumed to descend from * root. Otherwise returned path is null. */ static String makeRelative(Path root, Path absPath) { if (!absPath.isAbsolute()) { throw new IllegalArgumentException("!absPath.isAbsolute(), absPath=" + absPath); } String p = absPath.toUri().getPath(); StringTokenizer pathTokens = new StringTokenizer(p, "/"); for (StringTokenizer rootTokens = new StringTokenizer(root.toUri().getPath(), "/"); rootTokens.hasMoreTokens(); ) { if (!rootTokens.nextToken().equals(pathTokens.nextToken())) { return null; } } StringBuilder sb = new StringBuilder(); for (; pathTokens.hasMoreTokens(); ) { sb.append(pathTokens.nextToken()); if (pathTokens.hasMoreTokens()) { sb.append(Path.SEPARATOR); } } return sb.length() == 0 ? "." : sb.toString(); }