When do I use protected methods. Why can't I use public / private methods instead? about 2122-s2

[haoyangw]

Private methods cannot be accessed or extended/inherited by any other class, so if your method is designed for use by other classes/clients, you probably don't want to declare it as private.

Protected methods can be called from any subclass as well, so if you want your methods to be accessible from any subclass, not just those in the same package, protected is suitable. E.g. if you want to declare methods that can be called/inherited and overridden by a subclass outside your package.

Public methods have no restrictions on access, so for security you should only declare a method as public when absolutely necessary(i.e. breaks code/programs when you use private/default/protected). Most of the time our code won't need public access right now anyway, so there's no benefit in declaring methods as public either.

Personally, I think choosing precisely the correct access modifier for your functions(rather than using only private/public) is helpful for you to kind of evaluate your program/code logic since it makes you think about/evaluate who should/shouldn't be running what code so you understand the code you're writing better too.

[jlee1007]

Public methods can be accessible by everyone, within or outside the class, whereas private methods can only be used within the particular class where it is defined.

Protected methods provide a balance between private and public methods. Protected methods can be accessed within the class, or by its sub-classes, or classes within the same package. On the other hand, anyone outside of this scope will not be able to access the method e.g. Client won't be able to access the method. It is often used when you want to compare/ get information from different class objects without wanting to let your client see/access the code.

[Swagston20]

Try not to use protected at all. This is because it gives access to propertiesand methods to other class within the same package which breaks the principle of immutability.

[weekiatism]

To adhere to abstraction, having the appropriate access modifiers to ensure the hiding of certain methods and variables is needed.