Confusion on when to use private vs protected fields

Question

I have seen users in SO saying that protected fields are bad, because it can introduce problems as the code grows. Please refer to the following code.

public class Car {
    private String modelName;
    private int yearReleased;

//getters and setters

}

If the Car class is extended by a class named ToyotaCar

public class ToyotaCar extends Car{
   // Toyota specific stuff
}

I want my ToyotaCar object to have a modelName and yearReleased fields. And that is why I decided to extend from Car class. But private members are not inherited by the subclass (even though I could access those fields using a public getter and setter). Now my confusion is whether I should make the fileds in the Car class to protected instead of private. But people say that introduces problems.

Does it mean no matter what class you write always, make the fields private?

If so on what instances the protected keyword is used? is it only for methods which we are planning to use in our subclasses?

Answer 1

You nailed it yourself: a good practice is to make everything 'private' by default. Then, your specific design may require for example to be able to use some attributes or (preferably) some methods inside a subclass. In that situation, you'll need to move them toward 'protected' - but only in that situation.

Remember that using the accessors (getters & setters) is perfectly ok, and can be done without breaking encapsulation.