Java help (I know, I know java sux lol)

I'm trying to take a line in single character input and if it's uppercase, switch it to lower case and vice versa.
System.out.print ("Enter character: "); 
             s=stdin.readLine();
             c[i]=s.charAt(0);
             k=(int)c[i];
             if(k>96)
        {
                Character.toUpperCase(c[i]);
        }
             else
        {  
                Character.toLowerCase(c[i]);
        } 
             i++;
         }
         while(k!=46);

Everything else works right, but that doesn't flip it. HALP
<3

>>5-6
I no longer have enough faith in humanity left to believe that this is a deliberate troll. ：（