Override "private" method in java

Question

There something ambiguous about this idea and I need some clarifications.

My problem is when using this code:

public class B {      private void don() {         System.out.println("hoho private");     }     public static void main(String[] args) {         B t = new A();         t.don();     } }  class A extends B {     public void don() {         System.out.println("hoho public");     } } 

The output is hoho private.

Is this because the main function is in the same class as the method don, or because of overriding?

I have read this idea in a book, and when I put the main function in another class I get a compiler error.

Answer 1

You cannot override a private method. It isn't visible if you cast A to B. You can override a protected method, but that isn't what you're doing here (and yes, here if you move your main to A then you would get the other method. I would recommend the @Override annotation when you intend to override,

class A extends B {     @Override     public void don() { // <-- will not compile if don is private in B.         System.out.println("hoho public");     } } 

In this case why didn't compiler provide an error for using t.don() which is private?

The Java Tutorials: Predefined Annotation Types says (in part)

While it is not required to use this annotation when overriding a method, it helps to prevent errors. If a method marked with @Override fails to correctly override a method in one of its superclasses, the compiler generates an error.

Answer 2

is this because the main function is in the same class as the method "don"

No, it's because A's don() is unrelated to B's don() method, in spite of having the same name and argument list. private methods are hidden inside their class. They cannot be invoked directly by outside callers, such as main method in your case, because they are encapsulated inside the class. They do not participate in method overrides.