casting

[dolly shah]

public class X {
    void go(){
    System.out.println("x");
} }
            class Y extends X  {
                void go(){System.out.println("y");}
}
 

class Z extends X  {
                void go(){System.out.println("Z");}
}
     class Chrome2{
         public static void main(String...args){
             X z=new Z();
             X y=new Y();
             Z y2=(Z)y;//line 1
             z.go();
             y.go();
             y2.go();
         }
     }

Z & Y are sibling objects here. Line 1 fails at runtime but why it compiles?

[ahmed yehia]

Z y2 = (Z)y; //line 1

'y' is a variable of type 'X' that refers to an object of type 'Y' and you are casting it to type 'Z' which is a sub class of 'X' so it pass at compile time. Had it been of type 'Y' Not 'X' then it wouldnt compile.

[dolly shah]

Thanks Ahmed I got it. I was little confuse.

[yogesh sood]

Dolly,

You should have look at this from Corey, to understand how it works for Interfaces.

[camilo lopes]

You can not convert a car on a bike, only because both are vehicles. See the problem that prevents the compiler?
I hope I have helped!