Free Practice Quiz Question List

2 Classes and Objects Online Quiz Questions

Use this free practice quiz with 20 questions to review 2 Classes and Objects, test your knowledge, and prepare for your next test or exam.

20 questions

Choose one

1 point

Which statement best distinguishes a class from an object in object-oriented programming?

A
The class is a particular instance, while the object is a template.
B
The class is a template, while the object is a particular instance.
C
The class stores only data, while the object stores only behavior.
D
The class exists only after an object has been created.

Choose all

1 point

Which two statements correctly describe fields in a class? Select all that apply.

A
An instance field can hold a different value for each object.
B
A method cannot change an object's state.
C
A static or class field may be shared by all objects of the class.
D
A constructor is an ordinary field used to store state.

True or false

1 point

True or false: After checking.deposit(100), the savings object in the example also has a balance of 600.

A
True
B
False

Written response

1 point

What programming term means creating an object from a class?

Fill in the blank

1 point

A is a special operation used to establish an object's initial state when the object is created.

Choose one

1 point

A class includes a method named withdraw that validates an amount and may change the balance. What is withdraw?

A
A value that uniquely identifies a memory address and cannot change
B
A storage location that always belongs to the class rather than an object
C
A function defined as part of a class that provides behavior
D
A required argument supplied only when a class is declared

Choose all

1 point

Which two responsibilities are appropriate for a constructor? Select all that apply.

A
It establishes the object's initial state.
B
It must return an ordinary result such as a Boolean.
C
It is used only after the object has finished initialization.
D
It can help ensure that class invariants hold for the new object.

True or false

1 point

True or false: If first = checking and second = checking, then second.deposit(50) can change the balance observed through first.

A
True
B
False

Written response

1 point

What programming term describes keeping fields private and exposing carefully designed methods to control access to object state?

Fill in the blank

1 point

Two account objects can have equal account numbers and balances yet still be different because their object differs.

Choose one

1 point

In the lifecycle described, which condition indicates that an object has lost reachability?

A
The object has just been allocated but has no fields.
B
The object has been initialized but has never had a method called.
C
The object has equal field values to another object.
D
No live part of the program can reach the object through a reference.

Open ended

1 point

Using the Counter example, explain why counterA.currentValue() prints 4 after counterB.increment(). Your answer should address references, object identity, the instance field value, and the effect of the method call.

Written response

1 point

In the Counter example, what integer does counterA.currentValue() return after counterB.increment()?

True or false

1 point

True or false: In a garbage-collected language, an object that is no longer reachable is necessarily reclaimed immediately.

A
True
B
False

Written response

1 point

In the pseudocode methods for BankAccount, what keyword refers to the current object in an expression such as this.balance?

Choose one

1 point

A BankAccount object must store its own balance independently of every other account. Which kind of member should represent that balance?

A
A field that stores a value shared by every object
B
A field that belongs separately to each object
C
A method that initializes an object
D
A reference that identifies the class definition

Choose one

1 point

Why should a constructor validate an account's opening balance when a new BankAccount is created?

A
To compare two existing objects for identity
B
To release all external resources immediately
C
To establish the new object's initial state
D
To make every field static

Choose one

1 point

Which statement correctly distinguishes an instance method from a class or static method?

A
An instance method operates on a particular object
B
An instance method must always modify a static field
C
A class method requires a particular object for every call
D
A class method can only return a Boolean

Choose one

1 point

A BankAccount has a balance of 400. Its withdrawal operation returns false when the amount is less than or equal to 0 or greater than the current balance; otherwise, it subtracts the amount and returns true. Which call succeeds?

A
withdraw(0)
B
withdraw(250)
C
withdraw(-20)
D
withdraw(450)

Choose one

1 point

A BankAccount starts with a balance of 500. It performs withdraw(150) and then withdraw(300), and both operations are permitted. What is the final balance?

A
350
B
200
C
50
D
-100