wildcards again....

[Vishwanath Krishnamurthi]

Hi friends,

In the boldened line in this code, doesn't <?> get substituted with <Apple> during compile time? (I was thinking it would...)

The compiler shows me an error for using the next statement...

Basket.java:18: setElement(capture of ?) in Basket<capture of ?> cannot be appli
ed to (Apple)
b5.setElement(new Apple());

public class Basket<E>
   {
    private E element;
 
    public void setElement(E x)
     {
      element = x;
     }
   
   public E getElement()
   {
      return element;        
   }
 
   public static void main(String[] args)
      {
             [B]Basket<?> b5 = new Basket<Apple>();[/B]  //changing this to 
                                                         //Basket<Apple> is
                                                      //as expected.      
             b5.setElement(new Apple());  //gives an error here saying its
                                          //not applicable
             Apple apple = (Apple) b5.getElement();
             System.out.println(apple.aa);
      }
 
}
 

class Fruit {}
class Apple extends Fruit {String aa="Hi";}
class Orange extends Fruit {}

[Keith Lynn]

No it doesn't get substituted with Apple.

b5 is a reference to a Basket that can contain anything.

The problem is that it could also refer to a Basket that contains a class that isn't an Apple or a superclass of Apple.

So you can't safely add an Apple to it.

[Rahul Shilpakar]

hey can anyone explain me why to use <? ...> while creating object.