path_normalize.java

public static String normalize(String text) {
    StringBuilder sb = new StringBuilder();
    int ci;
    int pi = -1;
    while ((ci = text.indexOf('/', pi + 1)) != -1) {
        if (ci == 0) {
            sb.append('/');
        } else {
            String s  = text.substring(pi + 1, ci);
            if (s.equals("..")) {
                int end;
                if (sb.length() > 1 && (end = sb.lastIndexOf("/")) != -1) {
                    int start = sb.lastIndexOf("/", end - 1);
                    sb.delete(Math.max(start, 0), end);
                }
            } else if (!s.isEmpty() && !s.equals(".")) {
                sb.append(s);
                sb.append('/');
            }
        }
        pi = ci;
    }
    if (pi > 1) {
        sb.append(text.substring(pi + 1));
    }
    return sb.toString();
}