Character cannot be deferenced

Question

what does character cannot be deferenced mean?
heres my code, i get 4 character cannot be deferenced errors.
import java.io.*;
class intputoutput
    public static void main (String[] args)
       InputStreamReader inStream = new InputStreamReader (System.in);
         BufferedReader stdin = new BufferedReader (inStream);
       System.out.println("Enter single characters");
           char i, o;
          String sinput, soutput;
          do
          sinput = stdin.readLine();
          i = sinput.charAt(0);
               if (i.isUpperCase())
               o = 'i' + 32;
               o.toString(soutput);
               else if ('i'.isLowerCase())
               o = 'i' - 32;
                  o.toString(soutput);
          System.out.println(soutput);
          while(soutput.compareTo(".")!=0);
}

Answer 1

okay, i got the problem, the class name was different than the filename, by mistake. but now, if i input a lowercase letter, it shows a capital "I" and if i put in an uppercase letter or a symbol (&, *, $...) it shows a "?".