about the usage of switch and case

[Steven Gao Song]

Please see the code below:

public class TestSwitch {
   public static void main(String[] args){
        final short x = 7;
        int i = 7;
        switch(i) {
           case 5:   
System.out.println("enter 5....");
break;
     case x:
System.out.println("enter x....");
                break;
         }
   }
}

After compiling and execution, the result is

C:\>java TestSwitch
enter x....

I am a little bit confused: x is a short type, however i is an int type,
why it still can be compiled?

In K&B, they say --- A case constant must evaluate to the same type as the switch expression can use. Page 324


same type??