Why Can't a Subclass in Another Package Access a Protected Method?

Why can't a subclass in a different package access a protected method from its superclass?

In Java, the access modifiers dictate the visibility of classes, methods, and variables across different packages. The 'protected' access modifier allows visibility within the same package and also to subclasses located in different packages, but with specific conditions.

class SuperClass {
    protected void protectedMethod() {
        System.out.println("Protected Method in SuperClass");
    }
}

public class SubClass extends SuperClass {
    public void accessProtectedMethod() {
        // This will work since we are overriding the method.
        protectedMethod();
    }
}

Causes

• When a subclass is in a different package, it can only access the protected members of its superclass if it is instantiated.
• If the protected method is not overridden in the subclass, attempting to directly access it from the subclass that is in a different package will lead to a compilation error.
• The method's access is restricted to its class or instances of its subclasses; it cannot be accessed statically from another package.

Solutions

• To make a protected method accessible in a subclass from a different package, ensure that you instantiate the superclass or override the method in the subclass.
• If direct access is required, consider changing the access modifier of the method to 'public'.
• Alternatively, use public getter or setter methods to interact with the protected attributes.

Mistake: Trying to call a protected method directly from an instance of the superclass in a different package.

Solution: Always access the protected method through an instance of the subclass where possible.

Mistake: Assuming all methods in a superclass are accessible just by subclassing.

Solution: Remember to check the access level of the method in the superclass.