Why subclass in another package cannot access a protected method?

Question

I have two classes in two different packages:

package package1;

public class Class1 {
    public void tryMePublic() {
    }

    protected void tryMeProtected() {
    }
}


package package2;

import package1.Class1;

public class Class2 extends Class1 {
    doNow() {
        Class1 c = new Class1();
        c.tryMeProtected(); // ERROR: tryMeProtected() has protected access in Class1
        tryMeProtected();  // No error
    }    
}

I can understand why there is no error in calling tryMeProtected() since Class2 sees this method as it inherits from Class1.

But why isn't it possible for an object of Class2 to access this method on an object of Class1 using c.tryMeProtected(); ?

Answer 1

Protected methods can only be accessible through inheritance in subclasses outside the package. And hence the second approach tryMeProtected(); works.

The code below wont compile because we are not calling the inherited version of protected method.

 Class1 c = new Class1();
 c.tryMeProtected(); // ERROR: tryMeProtected() has protected access in Class1

Follow this stackoverflow link for more explaination.

Answer 2

I believe you misunderstand the difference between package and protected visibility.

package package1;

public class MyClass1 {
    public void tryMePublic() { System.out.println("I'm public"); }
    protected void tryMeProtected() { System.out.println("I'm protected"); }
    void tryMePackage() { System.out.println("I'm package"); }
}

• tryMePublic will be accessible wherever you are.
• tryMeProtected will be accessible to every subclass AND every class in the same package.
• tryMePackage will be accessible to every class in the same package (not available in children class if they are in a different package)

Children class in the same package

package package1;

public class Class2 extends MyClass1 {
    public void doNow() {
        tryMePublic(); // OK
        tryMeProtected(); // OK
        tryMePackage(); // OK
    }    
}

Children class in different package

package package2;

import package1.MyClass1;

public class Class3 extends MyClass1 {
    public void doNow() {
        MyClass1 c = new MyClass1();
        c.tryMeProtected() // ERROR, because only public methods are allowed to be called on class instance, whereever you are
        tryMePublic(); // OK
        tryMeProtected(); // OK
        tryMePackage(); // ERROR
    }    
}