Java generates a random number for a specified number of bits

Public class rondom { public static string genrandomnum (Int card_len) { &NBSP;&NBSP;&NBSP;//35 is because the array is starting from 0, 26 letters + 10 digits    final int maxNum = 36;    int i; //generated random number    int count = 0; //the length of the generated password    char[] str = {  ' 0 ',  ' 1 ',  ' 2 ',  ' 3 ',  ' 4 ',  ' 5 ',   ' 6 ',  ' 7 ',  ' 8 ',  ' 9 '  };   StringBuffer pwd = new  StringBuffer ("");    random r = new random ();    while (count  < card_len) {   //generates random numbers, takes absolute values, prevents the generation of negative numbers    i = math.abs ( R.nextint (Maxnum));  //generates a maximum of 36-1   if  (i >= 0 && i  < str.length)  {     pwd.append (Str[i]);      count ++;   }   }   return pwd.tostring ();} Public static void main (String[] args)  {for (int l=0;l<100;l++) {  System.out.println (Genrandomnum (6));//Generate 6-bit random number}}}

Java generates a random number for a specified number of bits