Getting confused by getting FileNotFoundException [duplicate]

Question

I've got that piece of code and just getting FileNotFoundException.

public class Overload {   
public void method(Object o) {     
    System.out.println("Object");   
    }   
public void method(java.io.FileNotFoundException f) {     
    System.out.println("FileNotFoundException");   
    }   
public void method(java.io.IOException i) {     
    System.out.println("IOException");   
    }   
public static void main(String args[]) {     
    Overload test = new Overload();     
    test.method(null);   
    } 
} 

Any thoughts why does it happen?

Answer 1

Because it does access the most specific method, which in this case is method(java.io.FileNotFoundException f)

inheritence order from FileNotFoundException

java.lang.Object -> java.lang.Throwable -> java.lang.Exception -> java.io.IOException -> java.io.FileNotFoundException.

As you can see, the IOException inherits from Object (at some point) which makes it more specific then Object. And the FileNotFoundException is more specific then IOException. In the end the compiler decides that it should call the method with the FileNotFoundException as parameter.

If there are two methods that are equally specific your code wouldn´t compile with the error that there is an ambiguous method call.