Software Testing Mutation Operators Example Codes

 Program1:Overriden Method Rename

Example of  :Overriden Method Rename

//List is a base class 

class List{

    void m(){

        f1();    //before the instance f(), if we rename it to f1()

    }

    void f1(){

        System.out.println("List::f()");

    }

}

//child class stack , it doesn,t have f1() method , f1() is not overriden

class Stack extends List{

    void f(){

        System.out.println("Stack::f()");

    }

}

public class Main{

public static void main(String[] args) {

//List l = new List();

//l.m();-----> output is List::f()

//Stack s = new Stack();

//s.m();-----> output is stack::f()

List l1 = new List();

List l2 = new Stack();

l1.m(); ------->output is List::f()

l2.m();------>output is stack::f()

}

}////After rename f() to f1() out put is     List::f()

                                                                List::f()

After rename f() to f1() output is List::f(), List::f() — is this correct?

Yes, that is correct — because f1() is not overridden in Stack.

Let me know if you want to see a version of the code with the output printed for both versions (f() and f1()) side-by-side.

Now Stack overrides f(), and dynamic dispatch will apply:

List l2 = new Stack();
l2.m();  // Output: Stack::f()

-------------------------------------------------------------------------------------------------

Key Concepts:

1. List.m() calls f1()

   • f1() is defined only in List.

   • f1() is not overridden in Stack.

   • Therefore, even if List l2 = new Stack();, calling l2.m() still invokes List.m(), which calls List.f1().

2. Stack defines f(), not f1()

   • So there's no method overriding of f1() in Stack.

3. Polymorphism doesn't apply here

   • Because f1() is not overridden, dynamic dispatch doesn’t occur for that method call.

   • So l2.m() will still use List's f1().

 Confusion Clarified:

You mentioned:

//Stack s = new Stack();
//s.m();-----> output is stack::f()

This is incorrect.
Since m() calls f1() (not f()), and Stack does not override f1(), it will call List's version of f1().