Question

I would like to know if somebody knows exactly what happens when the line of code comes to play:

class Class{}

class Math extends Class{}

class UseClasses{
public static void main (String[]args)

{

   new Math();  //Line 8
   (Class)new Math();//     Line 9

}

I thoroughly understand that the “new keyword” serves as object instance creator in the heap memory. However in the preceding bit of code you can see that line 9 makes an unusual use of this keyword (new). Line 8 it’s ok and compiles fine. but line 9 requires to assign the content to some other references. Thus this implies that each time the cast operand is present, in this case (Class)new Math, a new reference(underscoring reference and not object) is going to be instantiated.

Does it work in this way? If not, could you explain to me why it compiles fine in line #8 and it gives an error in line #9? (obviously due to the casting function not to be put there but why not?)

Answer 1

Since you don’t have referencing variable on line 9 compiler doesn’t consider this statement to be valid.

Cast is required when you have a referencing variable of a ‘more specific’ type that the object itself. For example, when you’re performing an upcast you don’t need it:

Class obj = new Math();

And you need an explicit cast when you’re performing downcast:

Class obj = new Math();
Math math = (Math) obj;