Array Initializer Doubt - Bert please explain..

[Jayant Raj]

Hi All,

Please help me out in understanding the following code :

  
public class Pizza {

   public static void main(String[] args) {

Pizza[] pizzas = new Pizza[10];  //Ok
Object objects = new Pizza[10];  //Ok.. Since Pizza[] is-a Object

Pizza[] pizzas2 = {new Pizza(),new Pizza()}; //Ok.. We are creating        
                      //an array of Pizzas & assigning the returned 
                      //reference to pizzas2
 
Object objects2 = {new Pizza(),new Pizza()}; // NOT OK. 
                      //Type mismatch: cannot convert from Pizza[] to Object
 
Object[] objects3 = {new Pizza(),new Pizza()}; // Ok..
}
}
 

Why is there a type mismatch while converting from Pizza[] to Object ? Also let me know whether Object[] is-a Object?

[Sebastien Col]

Hi,

The problem is that when you initialize a variable, the type of the init value must match the type of the variable.
Here, you have an Object type variable named "objects2" and you have a Pizza[] init value. Types don't match.

Arrays are extensions of the Object class. It is then possible to affect an array to an Object variable. The following code is valid:

Object[] objectsTab = {new Pizza(), new Pizza()};
Object obj = objectsTab;

I guess the difference is that during initialization, the JVM will allocated memory space to store the init value. I think that's why types must match, so that the JVM will have necessary information to allocate enough memory.

Sebastien

[Vlado Zajac]

 Object objects2 = {new Pizza(),new Pizza()} 

It the above code the compiler cannot determine the type of array to be cerated. It can be Pizza[] or Object[]. So statement like this is illegal.

The following code compiles without error.

 Object objects2 = new Pizza[] {new Pizza(),new Pizza()} 
 Object objects3 = new Object[] {new Pizza(),new Pizza()} 

[ August 25, 2005: Message edited by: Vlado Zajac ]