Choose the correct option to be included for the

Question

Choose the correct option to be included for the <access-modifier>

BlackTom AI · Accepted Answer

Java method overriding cannot reduce visibility: an overriding method must be at least as accessible as the method it overrides. This rule comes from Java’s access-modifier hierarchy (private < package-private (default) < protected < public).

Relevant knowledge points:
- protected methods are accessible to subclasses and to other classes in the same package.
- public methods are accessible everywhere.
- private methods are not visible to subclasses (so they cannot be overridden).
- When overriding, the subclass method’s access level must be the same or less restrictive (i.e., equal or more permissive).

Step-by-step reasoning:
1. In Shape.java the method is declared protected void display(). That establishes the minimum required visibility for any overriding method.
2. The Circle class extends Shape and attempts to override display(). The overriding method’s access modifier must be at least as permissive as protected.
3. public is more permissive than protected, so declaring public void display() in Circle is legal and increases accessibility.
4. protected is the same level, so declaring protected void display() is also legal.
5. Declaring default (no modifier / package-private) would be a reduction in accessibility (package-private is less permissive than protected) and is therefore disallowed by the compiler when overriding a protected method.
6. Declaring private is even more restrictive and cannot override a protected method at all.

Why the correct answer is correct:
Because both public and protected meet the requirement of being at least as accessible as the original protected method, they are valid choices for the overriding method in Circle.

Why other options are incorrect:
- “Only the public” is wrong because protected is also allowed.
- “Only the protected” is wrong because public is allowed too.
- “public, protected, and private” is wrong because private reduces visibility and cannot override a protected method (and default/package-private is also disallowed).

Conclusion: public and protected both can be used. This matches the provided answer.

Choose the correct option to be included for the <access-modifier>单项选择题

类似问题

When using inheritance, fields of the superclass are typically declared as:

The protected access modifier allows access from:

A sub-class has no access to private instance variables of its super class.

____________ access modifier is only visible in parent and child class, but not in other packages.

____________ access modifier is only visible in parent and child class, but not in other packages.

_______ is the access specifier to make a class member accessible only within the same class.

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