Which class members should have protected modifier?

Question

I know what the Java protected keyword is, that it is accessible to the class, package, subclass, but not the world.

My question is, when should I use protected?

Answer 1

You use protected in a class that is intented to be used as a base class and you want to access some methods or attributes from the derived classes even if they are not in same package and without making them public.

It is commonly used in frameworks. There is generally an interface that defines the public API, and a base class (often abstract) that is intended to be derived. In the derived class, the overriden methods may make use of some protected methods and or attributes. That way :

• those methods need not be public
• the derived class may be in implementor's package not in framework one.

Answer 2

You should use protected in that case, when you want the element to be accessible to the class, package, subclass, but not the world. This is very useful, if you make the program whit a large number of other programmers and you don't want them to change your variables but you want to be able to make subclasses which can do that.