Anonymous Inner Class

[dennis zined]

Hello.
In my anonymous inner class (pls. see code below), i override method1() and then call a newly defined method2() also within the anonymous inner class. Executing method1 from outside the anonymous inner class via a reference variable works just fine. However, executing method2 also from the same reference variable is not visible and results in compile error. How come method1 can see method2 but is not visible from the outside/reference variable?

  
public class Test {
    private SomeObject somekindofobject = new SomeObject() {
        public void method1(){
            System.out.println("some kind of method");  // overrides original method def.
            method2();                                  // Can call newly defined method2().
        }
        public void method2(){
            System.out.println("new method!!!");        // new method definition
        }
    };

    public static void main(String[] args) {
        Test test = new Test();
        test.somekindofobject.method1();                // ok! Executes new method definition
        //test.somekindofobject.method2();              // Compile Error!  Why?
    }
}
class SomeObject {
    public void method1(){
        System.out.println("method1");
    }
}

[Steve Lovelace]

The variable containing your anonymous class is of type SomeObject. Looking at SomeObject, you can see that it only has one method defined: method1(). As far as any class using a 'SomeObject' is concerned, this is the only method it has.
While the anonymous class is a subclass with method2() defined, it has no visibility (outside of the expression in which it is created), i.e., there is no type exposing method2() for any other code to see.
You could do something like this:

(new SomeObject() {
void method2() {System.out.println("hello");}
}).method2();  

and "hello" will print, but there is no other point in the code, other than inside the anonymous class, where method2() can be seen.
[ November 19, 2003: Message edited by: Steve Lovelace ]

[dennis zined]

Thanks Steve!

[Uma Balu]

Hi,
In your code, somekindofobject is actually an instance of SomeObject class, and method2 is not defined in the class SomeObject, it is supposed to be a new method of the anonumous class, hence it is not visible to somekindofobject (instance of SomeObject) .
Thanks,
Uma.

[dennis zined]

Also got this answer from K&B book:
Polymorphism is in play when anonymous inner classes are involved. Declaring anonymous inner classes is using a super class reference variable type to refer to a subclass object. As such, you can only call methods on an anonymous inner class reference that are defined in the reference variable type.