Anonyms Inner Class ????

[RAGU KANNAN]

Hello Folk's,

I would like to know how to call the anonyms innter class and the below example how can i call the method "sizzle". Pls explain to me.

Thanks, Raghu.K

class Popcorn {
    public void pop() {
        System.out.println("popcorn");
    }
}
 
class Food {
    public static void main(String argu[]){
 
        Popcorn p = new Popcorn() {
            public void sizzle() {
                System.out.println("anonymous sizzling popcorn");
            }
            public void pop() {
                System.out.println("anonymous popcorn");
            }
       };
   }
}

[ September 13, 2006: Message edited by: Barry Gaunt ]
[ September 14, 2006: Message edited by: Barry Gaunt ]

[Keith Lynn]

You won't be able to call it with the p reference. Since sizzle() is not defined in Popcorn, you can't call it on an instance of the anonymous inner class.

[Neelesh Bodas]

You can't.

Note that the only way to access an "anonymous inner class" is through the reference of the super class (Popcorn in the current case.) Since Popcorn class doesnot know "sizzle" method, there is no way you can call sizzle method on the anonymous inner class just created.

[Barry Gaunt]

Raghu, [B]please use

tags around properly formatted code,[/B] it makes youe example so much easier to read and understand.

[Febian]

Hope this answers your question!!!

import java.lang.reflect.*;
class Popcorn {    
public void pop() {        
System.out.println("popcorn");    
}
} 
 
class Food {    
public static void main(String argu[]) throws Exception {         
Popcorn p = new Popcorn() {            
public void sizzle() {                
System.out.println("anonymous sizzling popcorn");            
}            
public void pop() {                
System.out.println("anonymous popcorn");            
}       
};   
p.pop();

//p.sizzle(); //You can't do this because p is of type Popcorn 

//Solution 1, Downcast to the sub class  which is declared as anonymous.
((Food$1)p).sizzle(); 

//Solution 2, Reflect
Class clazz = p.getClass();
Method m = clazz.getDeclaredMethod( "sizzle", new Class[0] );
m.invoke( p, new Object[0] );
}
}

Note:
Please do not tell you are getting an error like the one below
>>>Food.java:23: cannot resolve symbol
symbol : class Food$1
location: class Food
perchance you meant 'Food.1'
((Food$1)p).sizzle();
^
1 error
> Terminated with exit code 1.

---
I am sure my code is correct will work.
Well! if you found the answer share it in the forum.

Happy Homeworking
[ September 14, 2006: Message edited by: febians sh ]

[Srinivas Kalvala]

Hello,

First overridding means, you are defining a method which is of same signature of your parent method. In your Anon. Class the sizzle() is not an overriding method and you are assiging it to Pop type, so you can't access it.

Remember:

1) Reference type super class can't access, new methods of its subclasses.
2) Reference type attributs always referes to Class type of reference.
3) Reference type methods alwyas referes to Reference type class even type is of Super Class.

I know they are confusing, but just read three times.

[Barry Gaunt]

"febians sh", please read our JavaRanch Naming Policy and change your displayed name to comply with it. The correct format for a displayed name is <first name or initials for first names><space><family name> and we prefer it if you use your real names.

Thanks
-Barry

[Barry Gaunt]

Originally posted by febians sh:

 
//Solution 1, Downcast to the sub class  which is declared as anonymous.
((Food$1)p).sizzle(); 

//Solution 2, Reflect
Class clazz = p.getClass();
Method m = clazz.getDeclaredMethod( "sizzle", new Class[0] );
m.invoke( p, new Object[0] );
 

Your first solution is a hack - you should not require a successful compilation without the hack so as to get the hack to compile. Also it goes against Sun's recommendations to use knowlege of anonymous classes generated by the compiler.

The second solution using Reflection is correct but that is beyond the scope of SCJP.

For SCJP examination purposes the answer is "you cannot call sizzle() through the reference to the anonymous class".
[ September 14, 2006: Message edited by: Barry Gaunt ]

[Shailesh Kumar]

You could invoke the sizzle method like this, but not much of use though.

    
class Popcorn {
    public void pop() {
        System.out.println("popcorn");
    }
}
 
public class Food {
    public static void main(String argu[]){
 
         new Popcorn() {
            public void sizzle() {
                System.out.println("anonymous sizzling popcorn");
            }
            public void pop() {
                System.out.println("anonymous popcorn");
            }
       }.sizzle();
       
       
   }
}

[Barry Gaunt]

That's a good catch, but it works only once because the new object goes poof after the call (I suppose it really gets sizzled in that case).

[RAGU KANNAN]

Hello Folk's

Thanks for all your reply I understood the concept.

Barry Gaunt,
sure, I will format the code next time.

Regard's Raghu.K