C [i] [i] = +1; Why not? Invited!

Abstract: c [i] [i] = +1; Why not? Invited!

Import java.io. *;
Public class Test7
(
Public static void main (String [] args) (

BufferedReader br = new BufferedReader (new InputStreamReader (System.in));
String str = "";
Try (
Str = br.readLine ();
)
Catch (IOException ex) (
System.out.println (ex);
)

Char c = new char [] [str.length ()];
C = str.toCharArray ();
For (int i = 0; i (
If (c [i] == 'z')
(
System.out.println ( "a");
)
Else
(
C [i] + = 1;
If //———- replaced c [i] [i] = +1 not to be ?—————-
)

)
String str2 = new String (c);

System.out.println (str2);
)
)

Why? Thank you