Do Java Subclasses Inherit Private Fields?

Do Subclasses Inherit Private Fields: A Java Conundrum

In Java, the concept of inheritance is often straightforward. However, the topic of private fields in subclasses introduces some ambiguity.

Question:

Do subclasses inherit private fields from their parent classes?

Initial Answer:

Based on the "normal OOP way" of object-oriented programming, the answer would be "No." Private fields are typically inaccessible to subclasses.

Java Documentation:

The Java Language Specification (JLS) states that "Members of a class that are declared private are not inherited by subclasses of that class."

Interviewer's Argument:

Despite the JLS quote, some may argue that private fields are inherited by subclasses, albeit indirectly. They claim that these fields exist within subclass objects and can be accessed through reflection or other means.

Arguments in Support of Interviewer:

• Object Composition: An object of a subclass must logically contain all of the fields inherited from its parent class, including private fields.
• Reflection API: Private fields can be accessed using the Java Reflection API, which gives classes the ability to inspect and modify their own and other class metadata.

Clarification from JLS:

The key distinction here is between inheritance for objects and inheritance for classes.

• Object Inheritance: Objects of subclasses contain instances of their parent class's private fields, even though these fields are inaccessible to the subclass.
• Class Inheritance: Classes themselves do not inherit private fields. Subclasses have no notion of their parent class's private members.

Conclusion:

While objects of subclasses inherit private fields from their parent classes, the subclasses themselves do not. This distinction between object-level inheritance and class-level inheritance is crucial to understanding Java's inheritance model. Despite the interviewer's argument, the JLS provides an unambiguous definition on the matter.

The above is the detailed content of Do Java Subclasses Inherit Private Fields?. For more information, please follow other related articles on the PHP Chinese website!