Inheritance

Question 1

How many superclasses can be specified for a subclass?

Answer 1

One

Question 2

Can a subclass access private members of its superclass?

Answer 2

No. inheritance doesn’t overrule private access restriction.

Question 3

Accessor methods

Answer 3

Provide access to private members of a class

Question 4

Which constructor creates an object given class inheritance?

Answer 4

The superclass constructor creates the superclass portion of the object & the subclass constructor creates the subclass portion.

The superclass portion of the object is constructed automatically using its default constructor.

Question 5

How can a subclass call a constructor defined by its superclass?

Answer 5

super()

Question 6

In a multilevel hierarchy, which constructor will superclass refer to?

Answer 6

The constructor in the closest superclass

Question 7

How can you access superclass methods?

Answer 7

Super()

Question 8

When are constructors executed in a class hierarchy?

Answer 8

Constructors execute in order of derivation from superclass to subclass

Question 9

Can a reference variable of a superclass be assigned a reference to an object of a subclass?

Answer 9

Yes

Question 10

Reference variable

Answer 10

Used to refer to an object

Question 11

Can reference variables refer to objects of different class types?

Answer 11

No

Question 12

What members do you have access to with a superclass reference variable?

Answer 12

The parts of the object defined by the superclass

Question 13

How do you construct a copy of an object?

Answer 13

Define a constructor that takes an object of the class as its parameter

Question 14

Method Overriding

Answer 14

When a method in a subclass has the same return type and signature as a method in its superclass.

Question 15

When you call an overridden method in a subclass, which method is returned?

Answer 15

It will always refer to the subclass method

Question 16

How do you access the superclass version of an overridden method?

Answer 16

Use super.method()

Question 17

Are methods overridden if their signatures differ?

Answer 17

No, they are simply overloaded.

Question 18

Dynamic method dispatch

Answer 18

The mechanism by which a call to an overridden method is resolved at run time rather than compile time.

Known as run time polymorphism

Question 19

Why is Polymorphism useful?

Answer 19

It allows a general class to specify methods common to all derivatives, while allowing subclasses to define the specific implementation of some or all of those methods.

Question 20

Abstract Class

Answer 20

Defines methods for its subclasses but does not provide an implementation

Question 21

Abstract Method syntax

Answer 21

abstract type name(parameter);

Question 22

What is in the body of an abstract method?

Answer 22

Nothing - it has no body

Question 23

Where can abstract modifiers not be used?

Answer 23

static methods or constructors

Question 24

When must a class be declared abstract?

Answer 24

When it contains one or mor abstract methods

Question 25

Can an abstract class have objects?

Answer 25

No

Question 26

When a subclass inherits an abstract class, what must it do to not be declared abstract as well?

Answer 26

Implement all abstract methods

Question 27

Final

Answer 27

Modifier used to prevent:
a method from being overridden
a class from being inherited
a variable from being changed

Convention for finals is upper class names

Question 28

Object class Methods

Answer 28

Clone()
equals()
finalize()
getClass()
notify()
notifyAll()
toString()
wait()

Question 29

What is the purpose of the toString() method?

Answer 29

It returns a string description of the object

Many classes override this method to tailor a description of objects created