Creating Superclasses and Subclasses

AP Computer Science A· difficulty 2/5

// Design choice: a Car has an Engine and is a Vehicle.
public class Engine {}
public class Vehicle {}
// Which design is correct?
public class Car extends Vehicle {
    private Engine engine;
}

Which best describes this design?

A
$Car has-a Vehicle and has-a Engine$
B
$Car is-a Vehicle and is-a Engine$
C
$Car is-a Engine and has-a Vehicle$
D
$Car is-a Vehicle (inheritance) and has-a Engine (composition)$
check_circle

Explanation

Inheritance (extends) models is-a; an instance field models has-a. Car extends Vehicle (is-a) and contains an Engine field (has-a).

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