Free Practice Quiz Question List

8 Inheritance and Object-Oriented Design Online Quiz Questions

Use this free practice quiz with 20 questions to review 8 Inheritance and Object-Oriented Design, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

A Java superclass declares a method with the protected modifier. Which code can generally use that method?

A
Only the declaring class
B
The declaring class, same-package classes, and subclasses under Java's protected-access rules
C
Any class in any package
D
Only subclasses, never same-package classes

True or false

1 point

A subclass automatically receives direct access to every private field declared in its superclass.

A
True
B
False

Written response

1 point

What design principle combines an object's state with its behavior and limits direct access to its internal representation?

Fill in the blank

1 point

In Java, a subclass declaration uses the keyword to identify its superclass.

Choose one

1 point

A Car object contains an Engine object and delegates some work to it. Which relationship best describes this design?

A
Inheritance, because every reused class should be a superclass
B
Overriding, because the engine supplies behavior
C
Composition, because a car has an engine
D
Polymorphism, because the car can call engine methods

Choose all

1 point

Which statements correctly describe Java method overriding? Select all that apply.

A
Its name and parameter types match the inherited method's signature
B
It cannot reduce the inherited method's visibility
C
It must be declared static
D
Its return type is the same type or a permitted subtype
E
It must replace a private method in the superclass

True or false

1 point

In Java, a static method is overridden in the same runtime-polymorphic way as an instance method.

A
True
B
False

Written response

1 point

An HourlyEmployee has an hourly rate of $25.00$ and has worked $160$ hours. According to its calculatePay() implementation, what numeric pay value should it return?

Fill in the blank

1 point

Polymorphism lets code work through a while selecting the appropriate overridden method at .

Choose all

1 point

Which design choices are recommended by the material? Select all that apply.

A
Keep fields private when outside code should not modify them directly
B
Use inheritance whenever it permits code reuse, even without an is-a relationship
C
Prefer composition when one object has or delegates to another object
D
Use @Override when intentionally replacing an inherited instance method
E
Branch on every concrete subclass before calling its behavior

Open ended

1 point

You are designing a BankAccount class whose balance must never be negative. Explain how encapsulation should shape its fields and methods, and explain how a subclass could obtain balance-related behavior without depending directly on the stored field.

Choose one

1 point

Which statement correctly distinguishes method overriding from method overloading?

A
Overriding uses different parameter lists and is selected at compile time
B
Overriding supplies a subclass implementation with a matching signature; overloading uses different parameter lists
C
Overloading is only possible when a method is inherited
D
Overriding applies to static methods but not instance methods

Choose one

1 point

A superclass marks one instance method as final but remains subclassable. What is the direct effect on that method?

A
It forces every subclass to call the method with super
B
It changes the method into a static method
C
It prevents subclasses from overriding the method
D
It makes the method private

Choose one

1 point

When evaluating whether a proposed subclass is a valid subtype, which question best applies the material's substitutability principle?

A
Whether the subclass exposes more fields than the superclass
B
Whether the subclass can be used where the superclass is expected without surprising the client
C
Whether the subclass reuses at least one line of superclass code
D
Whether the subclass has a different constructor name

Choose one

1 point

A BankAccount class must preserve the invariant that its balance is never negative. Which design best supports that requirement?

A
Make balance public so every client can update it.
B
Keep balance private and expose validated operations such as deposit and withdraw.
C
Make balance protected so every subclass can assign any value.
D
Remove the balance field and let clients store it themselves.

Choose one

1 point

A Java field stores an implementation detail that should be accessed only by methods in its declaring class. Which access level is the most appropriate?

A
public
B
protected
C
private
D
package-private

Choose one

1 point

A Car object contains and uses an Engine object. Which object-oriented relationship most accurately describes this design?

A
Inheritance, because both classes represent objects
B
Method overriding, because the car may call engine methods
C
Composition, because a car has an engine
D
Polymorphism, because an engine can be replaced

True or false

1 point

In Java, a static method in a subclass is hidden rather than overridden.

A
True
B
False

Written response

1 point

A Temperature object stores $100$ degrees Celsius and converts it with the formula $C \times \frac{9}{5} + 32$ . What value in degrees Fahrenheit does toFahrenheit() return?

Written response

1 point

A SalariedEmployee has an annual salary of $72000$ , and its calculatePay() method returns the annual salary divided into 12 equal monthly payments. What monthly pay does it return?