Understanding the 'protected' Access Modifier in Java

In Java, access modifiers are used to set the visibility and accessibility of classes, interfaces, variables, and methods. The 'protected' access modifier is one such keyword, and based on the quiz question given, the correct use of 'protected' in Java is "To provide access to the class members within the same package and subclasses."

The 'protected' access modifier in Java strikes a balance between the most restrictive 'private' modifier and the least restrictive 'public' modifier. A class member (fields or methods) declared as 'protected' can be accessed:

• Within its own class.
• Within classes in the same package.
• Within subclasses of its class, even if they are in a different package.

For instance, consider a Java class Animal defined in package animals with a protected method called eat(). Any other class in the animals package can access and call this eat() method. Simultaneously, any class that extends Animal, even if it's defined in a different package, such as pets, can also access and call the eat() method.

However, a class in a different package that does not subclass Animal won't be able to access the eat() method. So, the protected keyword gives more access than private, but less than public.

As per the best practices, use of the 'protected' modifier should be limited and done with caution. Overusing 'protected' can lead to increased coupling between classes, making the code harder to maintain. It's often better to keep data as 'private' and provide 'public' or 'protected' methods to manipulate this data, rather than making the data itself 'protected'.

Remember, an important principle in Object-Oriented Programming is Encapsulation, which emphasizes data hiding to ensure that class data is not directly exposed to other classes. In line with this, a class's internal state should only be exposed to other classes through methods, ensuring that other classes interact with it in an intended and controlled manner.

In conclusion, while 'protected' provides more visibility than 'private', it should be used sparingly and judiciously to maintain the robustness of your Java code.