The correct answer is private.
- Public variables are visible to all applications that use the instance of that class.
- Private variables are only visible to the class in which they are declared.
- Default variables are visible to the class in which they are declared and to any classes that inherit from that class.
- Static variables are visible to all applications that use the instance of that class, regardless of which class they are declared in.
Private variables are useful when you want to hide the implementation details of a class from other classes. This can make your code more modular and easier to maintain.
For example, let’s say you have a class called Car. The Car class might have a private variable called engine, which stores the car’s engine size. This variable would be hidden from other classes, so they would not be able to directly access it. However, the Car class could provide methods that allow other classes to get and set the value of the engine variable.
This would make it more difficult for other classes to accidentally modify the Car class’s internal state, and it would also make it easier to change the implementation of the Car class without affecting other classes that use it.