Reference Variable casting ... compile Errors vs Runtime errors

[karim amrani]

hi :
can you please tell me the rule to know wheather an upcast or a downcast will produce a compile error OR a runtime error , for exemple :

3. class Dog {
4.   public void bark() { System.out.print("woof "); }
5. }

6. class Hound extends Dog {
7.   public void sniff() { System.out.print("sniff "); }
8.   public void bark() { System.out.print("howl "); }
9. }

10. public class DogShow {
11.   public static void main(String[] args) { new DogShow().go(); }
12.   void go() {
13.   new Hound().bark();
14.   ((Dog) new Hound()).bark();
15.   ((Dog) new Hound()).sniff();     // [b]here's the problem[/b]
16.   }
17. }

i tought the it will produce "howl woof followed by an exception " BUT it produce a compile error at line 15 ..???

[Arjun Srivastava]

karim amrani wrote:
i tought the it will produce "howl woof followed by an exception " BUT it produce a compile error at line 15 ..???

welcome to ranch!!
go to edit and use code tags for writing codes.

because dog class doesn't know about the sniff() method, so it's a compiler error.
why do you think it should give a run-time exception?

[karim amrani]

because i dont know how to determines wich type of error it will raise ...so the MethodNotFoundException comes in my head and thought it's probably this .... that's why i asked you about A FIRM RULE to know if an error will be catched by the complier or while excution ..
thanks for the code-tag tip and Sorry for my english

[Arjun Srivastava]

no problem friend.
if compiler didn't able to find something that you are referring or using or some kind of syntactical mistake ,then it will gives you a compiler error.
exception will be thrown when your program satisfies the compiler needs,but some illegal behavior like illegal reference or argument you are using cause your program to stop at run time.