Changing Access Modifiers in Java Method Overriding

can we change the scope of the overridden method in the subclass in java? why?

In Java, when you override a method in a subclass, you cannot change the access modifier of that method to be more restrictive than the method in the superclass. However, you can change it to be less restrictive.

Access Modifiers in Java:

• public: The method is accessible from any other class.
• protected: The method is accessible within its own package and by subclasses.
• default (package-private): The method is accessible only within its own package.
• private: The method is accessible only within its own class.

Rules for Overriding:

1. Cannot be more restrictive: If the superclass method is public, the overriding method in the subclass cannot be protected or private. It can only be public or protected (or default if the superclass method is also default).
2. Can be less restrictive: If the superclass method is protected, the overriding method can be protected or public, but not private or default (if the superclass method is public).
3. Can be the same: You can keep the same access level as the superclass method.

Example:

class SuperClass {
    public void display() {
        System.out.println("Display from SuperClass");
    }
}

class SubClass extends SuperClass {
    // This is valid: same access level
    public void display() {
        System.out.println("Display from SubClass");
    }

    // This is valid: less restrictive
    protected void displayProtected() {
        System.out.println("Display from SubClass with protected access");
    }

    // This is NOT valid: more restrictive
    // private void display() {
    //     System.out.println("This will cause a compile-time error");
    // }
}

Conclusion:

You can change the scope of the overridden method in a subclass, but only to be less restrictive. This is to ensure that the polymorphic behavior of the superclass is preserved and that the subclass can be used in place of the superclass without breaking the contract established by the superclass's method visibility.