Should you ever use protected member variables? Depends on how picky you are about hiding state. If you don’t want any leaking of internal state, then declaring all your member variables private is the way to go. If you don’t really care that subclasses can access internal state, then protected is good enough. If a … Read more
When a class is (intended as) an abstract class, a protected constructor is exactly right. In that situation you don’t want objects to be instantiated from the class but only use it to inherit from. There are other uses cases, like when a certain set of construction parameters should be limited to derived classes.
Because it makes no sense. Protected class member (method or variable) is just like package-private (default visibility), except that it also can be accessed from subclasses. Since there’s no such concept as ‘subpackage’ or ‘package-inheritance’ in Java, declaring class protected or package-private would be the same thing. You can declare nested and inner classes as … Read more
Yes, because that’s not how you remove a range from outside code. Instead, do this: list.subList(start, end).clear(); This actually calls removeRange behind the scenes.† The OP asks why removeRange is not part of the List public API. The reason is described in Item 40 of Effective Java 2nd ed, and I quote it here: There … Read more
It’s more a stylistic thing than a direct problem. It suggests that you haven’t properly thought through what is going on with the class. Think about what static means: This variable exists at class level, it does not exist separately for each instance and it does not have an independent existence in classes which extend … Read more
You can bypass encapsulation with the send method: myobject.send(:method_name, args) This is a ‘feature’ of Ruby. 🙂 There was internal debate during Ruby 1.9 development which considered having send respect privacy and send! ignore it, but in the end nothing changed in Ruby 1.9. Ignore the comments below discussing send! and breaking things.
Private members are only accessible within the class defining them. Protected members are accessible in the class that defines them and in classes that inherit from that class. Edit: Both are also accessible by friends of their class, and in the case of protected members, by friends of their derived classes. Edit 2: Use whatever … Read more
You use: public scope to make that property/method available from anywhere, other classes and instances of the object. private scope when you want your property/method to be visible in its own class only. protected scope when you want to make your property/method visible in all classes that extend current class including the parent class. If … Read more
The official tutorial may be of some use to you. Class Package Subclass(same pkg) Subclass(diff pkg) World public + + + + + protected + + + + no modifier + + + private + + : accessible blank : not accessible