static String unquote(String s) {
  if (s == null) return null;
  if (s.startsWith("[")) {
    int i = 1;
    while (i < s.length() && s.charAt(i) == '=') ++i;
    if (i < s.length() && s.charAt(i) == '[') {
      String m = s.substring(1, i);
      if (s.endsWith("]" + m + "]"))
        return s.substring(i+1, s.length()-i-1);
    }
  }
  
  if ((s.startsWith("\"") || s.startsWith("\'")) && s.length() > 1) {
    int l = s.endsWith(substring(s, 0, 1)) ? s.length()-1 : s.length();
    StringBuilder sb = new StringBuilder(l-1);

    for (int i = 1; i < l; i++) {
      char ch = s.charAt(i);
      if (ch == '\\') {
        char nextChar = (i == l - 1) ? '\\' : s.charAt(i + 1);
        // Octal escape?
        if (nextChar >= '0' && nextChar <= '7') {
            String code = "" + nextChar;
            i++;
            if ((i < l - 1) && s.charAt(i + 1) >= '0'
                    && s.charAt(i + 1) <= '7') {
                code += s.charAt(i + 1);
                i++;
                if ((i < l - 1) && s.charAt(i + 1) >= '0'
                        && s.charAt(i + 1) <= '7') {
                    code += s.charAt(i + 1);
                    i++;
                }
            }
            sb.append((char) Integer.parseInt(code, 8));
            continue;
        }
        switch (nextChar) {
        case '\\':
            ch = '\\';
            break;
        case 'b':
            ch = '\b';
            break;
        case 'f':
            ch = '\f';
            break;
        case 'n':
            ch = '\n';
            break;
        case 'r':
            ch = '\r';
            break;
        case 't':
            ch = '\t';
            break;
        case '\"':
            ch = '\"';
            break;
        case '\'':
            ch = '\'';
            break;
        // Hex Unicode: u????
        case 'u':
            if (i >= l - 5) {
                ch = 'u';
                break;
            }
            int code = Integer.parseInt(
                    "" + s.charAt(i + 2) + s.charAt(i + 3)
                       + s.charAt(i + 4) + s.charAt(i + 5), 16);
            sb.append(Character.toChars(code));
            i += 5;
            continue;
        default:
          ch = nextChar; // added by Stefan
        }
        i++;
      }
      sb.append(ch);
    }
    return sb.toString();   
  }
  
  return s; // not quoted - return original
}

Began life as a copy of #1001735