Why can a class not be defined as protected?

Question

Why can we not define a class as protected?

I know that we can\'t, but why? There should be some specific reason.

Answer 1

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 protected or private, though.

Answer 2

Protected is not similar to public. Protected has both package level access plus can be accessed outside of packages only by inheritance..If a class say A outside a package INHERITS a class from other package(with protected method by using INHERITANCE) it can access the methods of this class B which has protected methods but the sub-classes derived from this class i.e., A can't access the protected methods..the opposite happens with public..

Example:

package 2;
class B
{
protected void method1()
{
}
}
package 1;
import 2.B;
class A extends B
{
//can access protected method
}
class C extends A
{
//can't access the protected method
}

Answer 3

behavior of “protected” = behavior of “default”+ “use it in any subclass in any package”.

Anyway we have default access modifier for class, only advantage we can get from protected access modifier is:- by using it in any package through subclassing. But for subclass, visibility of parent “protected”class would be private. So it can’t be accessed. Basically if you have a protected top-level class, no outer class can gain access by subclassing it. So protected for a top-level class is meaningless.

Answer 4

protected means that the member can be accessed by any class in the same package and by sub classes even if they are in another packages.

Example:

package a;
class parent{
 protected void p();
}
package b;
import a.p;
class child extends parent{
  //you can access method which is protected in the parent in the child 
}
class another extends child {
 //here you can not access the protected method 
}

Answer 5

public class A
{
    protected class B
    {
    }
}

Answer 6

What makes sense to this question is that, JVM is written in C (Sun JVM) and C++(oracle JVM) so during compilation, we are going to create .class files out of our java file and if we declare a class with Protected keyword then it will not be accessed by JVM.

The answer why protected class will not be accessed by JVM is that, since protected fields are accessible within same package or to diffrent package through inheritance only and JVM is not written in a way so that it will inherit will class. Hope this satisfies this question :)

Similarly, A top level class can't be private. Explanation as below:

So what will happen if we will define a class private, that class will only be accessible within the entity in which it is defined which in our case is its package?

So defining private access to the class will make it accessible inside the same package which default keyword already do for us, Therefore there is no benefit of defining a class private it will only make things ambiguous.