What does the protected modifier mean?

Question

I am reading the book The Java Programming Language, 3rd edition.

In chapter 3.5 , it illustrates the protected modifier with the following words:

More precisely, beyond being accessible within the class itself and to code within the same package, a protected member can also be accessed from a class through object references that are of at least the same type as the class that is, references of the class's type or one its subtypes.

The words makes me confused, in two aspects:

1. protected member can be accessed by code within the same package ? What I knew before is protected member can only be accessed by the subclass...

2. I don't understand what does a protected member can also be accessed from ... mean, anyone can explain to me please?

Solution 1

1. Yes, protected members can be accessed from the class itself, subclasses of the class and also all classes in the same package of the class (doesn't matter if those are subclasses or not). If you didn't know that last part before, then you've just learned something new.

2. It simply means that you can use those members; if a member is not accessible, it means you'll get a compiler error when you try to use it.

Solution 2

In Java, protected means that the member can be accessed by any class in the same package and by subclasses even if they are in another packages.

Note

A protected variable is not visible outside the package

for example B extends A and A has a protected int x; it can be use within the class B. But cannot be access using its instance variable

Solution 3

1) Yes, protected members can be accessed by classes from the same package. That's the way Java works.

2) That means subclasses can access them.