Generate x-bit random numeric password, CAPTCHA, character password

    1. Generate x-bit random numeric password public

    String getrandomnum (int length) {

        string num = "";
        for (int i=0;i<length;i++) {
            Integer a = (int) (Math.random () *10);
            num = num+a.tostring ();
        }
        Print results
        System.out.println (num);
        return num;
    }
    Can add to the logic of judgment.

    2. Generate random digit character password or authentication code public

    String getrandomstring (int length) {
            string str= "ABCDEFGHIJKLMNOPQRSTUVWXYZ123456 ";
            Random Random = new Random ();
            StringBuffer SBBF = new StringBuffer ();
            for (int i = 0; i < length; i++) {
                int number = Random.nextint (Str.length ());
                Sbbf.append (Str.charat (number));
            }
            System.out.println (Sbbf.tostring ());
            return sbbf.tostring ();
     }