38. OCR A Level (H446) SLR7 – 1.2 Object-oriented languages part

What does encapsulation mean in object-oriented languages?

• The bundling of data with methods that operate on and restrict direct access to it

• The process of inheriting properties from another class

• A function within a class

• A template for creating objects

Answer explanation

Encapsulation in object-oriented languages refers to the bundling of data with methods that operate on and restrict direct access to it.

Why is encapsulation used?

• To make code execution faster

• To increase the size of the code

• To hide the values of an internal state of an object

• To allow direct access to object attributes

Answer explanation

Encapsulation is used to hide the values of an internal state of an object, ensuring data integrity and preventing direct access to attributes.

How can encapsulated attributes of an object be accessed or changed?

• Using external functions only

• Via the methods provided by that object

• Through global variables

• Directly, by any part of the program

Answer explanation

The encapsulated attributes of an object can be accessed or changed via the methods provided by that object.

What is the main benefit of encapsulation?

• It makes the program run faster

• It allows unrestricted access to data

• It helps keep data related to an object safe

• It simplifies the code structure

Answer explanation

The main benefit of encapsulation is that it helps keep data related to an object safe.

What happens if another part of the program tries to alter an object's data without using its methods?

• The object is deleted

• The program crashes immediately

• It results in an error

• The data is altered successfully

Answer explanation

Trying to alter an object's data without using its methods results in an error because direct access violates encapsulation and can lead to unexpected behavior.

What analogy is used to describe private attributes in the context of encapsulation?

• Global variables

• Local variables

• Public methods

• External functions

Answer explanation

Private attributes in encapsulation are analogous to local variables, as they are only accessible within the class they are defined in.

What will happen if you try to directly access an object's private attributes?

• The access will be granted

• The attribute will become public

• The program will ignore the request

• It will result in an error

Answer explanation

Accessing an object's private attributes directly will result in an error as private attributes are not meant to be accessed outside the class.

How should an object's methods be set to allow access to its private attributes?

• Private

• Static

• Protected

• Public

Answer explanation

To allow access to private attributes, an object's methods should be set as public.

What does the example with 'person1.name = t' demonstrate?

• How to correctly change an object's attribute

• An error due to direct access to a private attribute

• The creation of a new object

• A successful method call

Answer explanation

The example with 'person1.name = t' demonstrates an error due to direct access to a private attribute, as private attributes should not be accessed directly.

What is required for a string to be accepted by the 'set name' method in the example?

• It must be exactly 1 character long

• It must be a numeric value

• It must be between 3 to 20 characters long

• There are no requirements

Answer explanation

The correct choice is 'It must be between 3 to 20 characters long' as this is the requirement for a string to be accepted by the 'set name' method in the example.