Which two statements are true about has-a and is-a relationships?

  1. Inheritance represents an is-a relationship.

  2. Inheritance represents a has-a relationship.

  3. Interfaces must be used when creating a has-a relationship.

  4. Instance variables can be used when creating a has-a relationship.


Correct Option: A,D
Explanation:

To understand the differences between has-a and is-a relationships, let's first define them:

  • Has-a relationship: This is a composition relationship between two classes where one class contains an instance of the other class as a member variable. It represents a "part-of" relationship.
  • Is-a relationship: This is an inheritance relationship between two classes where one class is a subclass of the other class. It represents a "kind-of" relationship.

Now, let's go through each option to understand why it is correct or incorrect:

Option A) Inheritance represents an is-a relationship - This option is true because inheritance is used to create a subclass that is a specialized version of the superclass. The subclass "is-a" kind of the superclass.

Option B) Inheritance represents a has-a relationship - This option is incorrect because inheritance does not involve composition between two classes. It is used to create a specialized version of an existing class.

Option C) Interfaces must be used when creating a has-a relationship - This option is incorrect because interfaces are not required to create a has-a relationship. A has-a relationship can be created using instance variables.

Option D) Instance variables can be used when creating a has-a relationship - This option is true because instance variables can be used to represent the composition relationship between two classes. One class can contain an instance of the other class as a member variable.

Therefore, the correct options are A and D.

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