public static boolean isUniqueChars(
      String s) {
    if (s.length() > 256) {
      return false;
    }
    int checker = 0;
    for (int i = 0; i < s.length(); i++) {
      System.out.println(s.charAt(i));
      int val = s.charAt(i) - 'a';
      System.out.println("val =" + val);
      System.out.println("checker =" + checker);
      System.out.println(String.format("checker= %32s", Integer.toBinaryString(checker)).replace(
          ' ', '0'));
      System.out.println(String.format("val= %32s", Integer.toBinaryString(val)).replace(' ', '0'));

      System.out.println(String.format("1<<val= %32s", Integer.toBinaryString(1 << val)).replace(
          ' ', '0'));

      System.out.println("(1<<val) = " + (1 << val));
      System.out.println("(checker & (1<<val) = " + (checker & (1 << val)));

      if ((checker & (1 << val)) > 0) {
        return false;
      }
      checker |= (1 << val);

      System.out.println(String.format("checker_after= %32s", Integer.toBinaryString(checker))
          .replace(' ', '0'));
      System.out.println("----------------------------------------");
    }

    return true;
  }