final reference variables K&B SCJP 6

[Harry Henriques]

Hello,

Please examine the code snippet below. I don't understand why K&B say that "reference variables must be initialized before the constructor completes." The code below compiles and runs just fine.

Thanks,

K&B Two Minute Drill Chapter 1 wrote:final variables have the following properties:
final variables cannot be reinitialized once assigned a value.
final reference variables cannot refer to a different object once the object has been assigned to the final variable.
final reference variables must be initialized before the constructor completes.

C:\temp>cat Final.java

class Reference {

   void thisReference() {
      System.out.println("ThisReference says hello");
   }
}


public class Final {

   public static void main(String [] args) {

       final int junk;

       final Reference referee;

       referee = new Reference();

       referee.thisReference();

       junk = 10;

       System.out.println ( junk );
   }
}

C:\temp>vi Final.java

C:\temp>gvim.exe Final.java

C:\temp>javac Final.java

C:\temp>java Final
thisReference says hello
10

[Jeanne Boyarsky]

That comment means final instance (or static) variables must be initialized before the constructor completes.